Here is a list of some of my ideas:
1. Darker town setting/music/atmosphere. This suggestion is purely a personal opinion but I thought I should state it anyway. Oblivion is hands down a dark game, yet I do not really feel this when walking through towns or speaking with townsfolk. There are 3 reasons for this:
a ) Town/City music seems pleasant, even uppity at times.[/u] Compare this with the next reason I have provided...
b ) Most of the races seem to be getting along just fine. These are people of various differences both physically and culturally, and a lot of them just seem to not care how that Hulking Orc just walks the streets at night, or that snobbish High Elf owns a shop nearby. I am not a fan of cruelty or playing bad characters, but I would love to step in and stop that band of nords from beating up that sole orc in town, just because of his differences. Or how about a gang of humans oogling over some pretty little wood elf female? What would you do if you saw a big warrior trying to forcefully take her outside with him? Moments like these can help create stark differences in the playstyle between good and evil characters. Just how good are you really, unless you thrown into some really bad situations? These can create memorable moments, but only if these experiences feel extreme enough to be real. Games like the Witcher left me with genuine feelings of sadness and emotion when I saw the various races reacting violently towards eachother, and I knew I could play a part in putting an end to that violence. This made me feel connected to the game world so much more.
c ) Townsfolk should have varying personalities towards the player character, with a large degree of indifference, unless you character is famous, and/or charismatic. As odd as this may sound, conversing with the residents of Tamriel should be a privilege, not an absolute certainty. See that pretty young Nord? She won't even speak to you unless you have sufficient personality/reputation. See that town guard? He will not offer you directions because he doesn't have to (start training personality, or building a reputation). See that big castle in the middle of town? Good luck getting in unless you have sufficient personality/reputation. Why do people even stop to look at me in the streets? Unless I am the hero of Kvatch, I should be a nobody to them. Npc characters should be indifferent, rude, or outright hostile towards me, unless I earn their respect. This is important with nobles in particular, who often offer quests with the greatest rewards.
2. Training. Training could be fun and profitable before going out on adventures, and can even be entertaining. I spend a lot of time already casting spells/jumping or anything I can do to better myself while in my current residence or the nearest guildhall. Why couldn't I train in some archery practice or swordsplay with a dummy next to my guildmates? Even better, why couldn't I purchase training equipment for one of my homes, so I could practice a little each day? Just like Oblivion, training can be limited to 5 times a level, or perhaps even maxed out at a particular skill level (such as 25) to prevent unbalancing. To me nothing is more satisfying and realistic than brushing up on my skills before a particularly daunting quest, even if the potential gains are limited. After training for free in the initial skill levels, perhaps trainers can then be employed for higher skill levels (25-75) at various costs.
3. No Place is safe (towns and cities). I read a post earlier about towns being attacked while the player character is present. I've always wanted this. Hordes of demons throwing themselves on the walls of a city (the attack can be regulated, with minimum level of civilian deaths and the monsters eventually killed off) can provide a lot of atmosphere and depth. Civilians could scream for help or call on you. See those 3 peasant women conversing on the road, walk a little closer only to see them suddenly ambushed by a group of snarling wolves. Towns can be a safe refuge (sometimes) during the day, but at night, the player's heart should quicken. Some quick points...
a) In Daggerfall, undead wraiths prowled the city at night, sometimes sneaking up on the player character as they were hard to spot in the darkness. I remember a few hits could send a low-level character to the grave. When playing in character these sorts of situations really generate a sort of panic. Why? Because in the darkness of night, your enemies have the upper hand, and could set an ambush, catching you completely off guard. In The Witcher, a particularly creepy looking monster (the vampyre, I believe?) would sometimes fly into town at night while you were travelling and attack you on sight. The initial shock alone could give a monster the upper had in a fight. If assassins were looking for you, they could attack from behind a building or shoot a crossbow bolt at you from a distance, making you wish you were indoors. If you cannot see the enemy, it's time to run for some cover, allowing for some intense moments.
b ) Oh, so you bought a house, how cute. One night while sleeping, you awaken to find a hooded assassin leering over you, perhaps even getting the first shot (poison, anybody?). One night, while practicing swordsplay in your hut, there is a loud banging on your door, and howling outside. If you are a low-level character, do you open it? What is out there? Better to just leave it... what if they broke in? I think the player character could have the option to invest in more powerful locks from merchants as the game progresses, eventually even magical wards and/or guardians. This could prevent random acts of breaking and entering by various enemies. When the character is not around, maybe even theft could be an option, but I realized this could be a gameplay element that may infuriate all but some of the most hardcoe players. However, just when you thought you were safe inside your little, newly purchased hut...
c ) Small farms usually dot the land of Tamriel. I think it would be interesting if, say, one day a family asks you to stay for dinner and when you do the farmstead is attacked by bandits. The character can tell the family to hide or fight. Or the character can hide, and watch the family slaughtered. How you choose to act determines the outcome. Higher levels include more fearsome foes, such as heavily equipped bandits, ogres, and the like. Just because I am inside of an npc's home doesn't mean I am safe. Or they are. Also, even though some of these npcs will sometimes die, giving them names and personality can create realism, and have an impact on the player character depending on whether he saves them or not. Watching Belle, the farmer's daughter being mauled by werewolves can be shocking, even upsetting if the player character cannot react to save her in time.
d ) I'm not sure how complicated it would be to create simulated battles in towns and cities (well, I imagine it will be quite complicated), maybe this can be done more for the surprising factor, the 'WOW" factor rather than just seeing important npcs dying left and right. People might miss that Argonian Trainer, but won't think twice about losing a few guards and/or carefully placed townsfolk (once again with actual names like Tom, or Brian. Not just Imperial Guard or Male Peasant) Perhaps certain areas can be designated as "death zones" and the designers can place various npcs whom they will not miss who can fight off enemies or die accordingly. Once again, this is all in the interest of creating a sense of the world being alive with or without the player's infuence. Maybe someone else can provide some better ideas, as I am at a loss for the moment.
4. I would like to see enemies create ambushes for me, especially in dungeons. If I am attacking a rogue hideout, or a vampire lair, I believe enemies should have an advanced warning of my approach, even if I am a deadly, quiet assassin. Say, if for instance I successfully kill a number of enemies in a given dungeon, some but not all of the remaining enemies create strategic ambushes or hide behind a corner and wait for me to approach before I attack. Nothing scarier than an invisible rogue attacking me from behind when I am unaware. Or a creature jumping from behind a rock to pummel me. It's an interesting idea to know enemies are planning surprise attacks and can cause the player character to tread carefully, even respect the enemy. Once again, stealth player characters should have many opportunities to provide their own ambushes as well, so not all the enemies need be too intelligent.
5. Invisibility is fun, unless the enemy is using it against you.
a ) Let's go back to a town setting again. "It is night time, and you are sitting in a quiet inn somewhere out in the wilderness. There are some patrons nearby, eating or drinking, and you sit down by the fire to warm your toes (or go to your room to rest, talk to the innkeep to barter, etc.) suddenly the screen flashes red as you realize you are being backstabbed by someone. You turn around to see nothing but the patrons running for the door. There are no enemies. You are attacked again. And again..." This unseen enemy is obviously using invisibility. If you do not have a spell of true seeing, or a potion of the same name, you must either wait for the enemies' spell to wear off or start swinging wildly hoping to see blood spill. If you run and try to hide in a room, you might be extremely cautious going back out again, thus creating real fear and immersion. Even if the enemy is relatively weak, with an invis spell for, say 5 sec, this can be enough to generate real panic in a player character if he is caught off guard.
b ) Invisibility is fun, unless it is easy to exploit. Enemies should not only become startled if they hear me when I am hidden, but should back up against the wall or swing their sword wildly. If they happen to hit me, they will know it by my shout, blood, etc., and can begin to attack me repeatedly, until I disengage and hide or kill them. More advanced enemies (even guards, or adventurer npcs) should carry potions of true seeing to reveal me should I fight like this. Invisibility is very fun when sneaking up on someone for the first time, and getting the initial blow. After that the enemies should have more ways (attacking wildly, potions, spells) to counter your offensive and fight back, allowing them a better chance, and creating more of a challenge. They should even be able to follow the sound of my footsteps while moving, and concentrate their attacks in that general direction, until they hit me.
6. Romance can be fun, along with some smaller side quests, and a possible side kick and/or companion to live in your house. High personality, and a decent reputation can bag you a nice companion to clean for you and cook in your home. There is nothing overly complex about the idea of having a simulated character performing menial tasks about town such as shopping, working, conversing with others, and then spending the night in your house. By the way, if the player character wishes to pursue a nightly romance, some sound effects, text, or screen fading to black is all that is needed to leave the rest to imagination. This is not necessary, no, but can once again leave the player with the impression that he is living in a simulated environment. If the character is so inclined, he can have two companions, or maybe more. Quests, side-missions, developing conversational threads, even sending your npc out on small missions (Go to work, please. Buy items. Collect alchemical ingredients. Spy on someone. Kill someone, etc, etc.) can be very fun. How about having them work at a nearby guild to increase your reputation with them? Even as a minor addition, this can lead to some fun ideas. The Witcher incorporated some of these elements, if on a different scale, and so did games like Dragon Age. Even the old Fallout games to some degree. In a simulated rpg world there should be some option for a simulated relationship, in my own personal opinion.
7. Last but not least, reputation should effect the amount of npcs who aproach you and quests given. As a the player progresses through the game, he achieves reputation. With reputation comes events such as..
a ) Potential allies/romantic interests. This gruff paladin could travel with you for some time, or even guard your house. Maybe he can protect the town you live in for added reputation and prestige. This young Nord woman could seek you as a potential suitor, and be willing to marry and move in with you. She can cook special potions/foods and/or provide defense for your home, etc.
b ) People from nearby at first, then from farther away as you progress in reputation and experience, call upon you for aid. They may stop you in the streets, and some come right to your home in the dead of night and knock on your door. They may even send couriers to seek you out with promises of reward should you aid them. When you walk around town, npcs begin to stop in their tracks, and gaze in awe at you, even offer you gifts and/or praises. They present you with trophies that can be mounted on the wall of your home, and can only be unlocked and certain reputation levels.
These are just some of the ideas I am thinking of, and I know there are better ones out there. So let's here them!