well, I guess I'll kick it off then. Some ideas I posted a long time ago, yet never actually did anything with them.
Inquiry Based Mapping- It seems unlikely that you would automatically know the name of every obscure/lost daedric ruin or dwemer stronghold (unless, of course, you just make it all up as you go along) or a town if you, say, intervention'd there or just wandered there for no particular reason. I think it would be cool if you had to ask people about where you were or could see a sign and get a journal entry saying "I marked suran on my map" or something. Also if you could speak to someone about background leading to "I'm a proud member of the noble *so and so* lineage" and you ask them about that which leads to "yes, we even have our own tomb, it's down the road to caldera on the right..." and when you walk there you will see the name of the tomb marked down, where as before it was masked (which evidently is impossible
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Cartographer's Guild- This one was coupled with the one above. In it there would be a new guild of mappers who are out to explore the world. The guild would potentially be a caravan that travels from town to town, but if not it can be buildings too. You would be sent on quests to go and map out a dungeon or daedric ruin where you would have to reach certain checkpoints to complete it. I think that would be fun to add a guild who's main focus is exploration.
Elusive creaturescreatures such as brownies and sprites who will turn invisible or teleport away when you come in a certain distance. perhaps hobgoblin camps where they are cooking some rat meat, but if on of them spots you, with a very large alarm radius, they will turn invisible and run. if you are stealthy or clever enough you may be able to catch them and partake on their valuable ingredients and hordes of magical trinkets. Creatures that I think would fit the spot are:
Pixies: Pixies are harmless creatures that are always busy and just want to tend to their own business. They will disappear at the first sight of humans and are extremely resistant to magic.
Hobgoblins: Will make small camps in the bitter coast and west gash regions. You may hear them and see their fires from a distance. Within a certain area (not invisible or sneaking) you will disturb them and both them and their camp will be teleported to safety. if you can manage to kill the leader (the one who will teleport everyone away, but has no obvious traits of a leader) the other two or three will try and run. their ingredient isn't very good or valuable, but in their camps they keep a chest full of silverware and various magical trinkets.
Brownies: They would be in houses, nearly entirely invisible, and (unless their master is dead) they will try and run to their master, but when they run they become visible again. If you can stop it from reporting your crime to it's master then you can get it's low level invisibility ring as well as brownie ears which are valuable and good for alchemy.
Doppleganger: This will hang around a group of creatures, but it's form will not be exactly the same as the others in the group and will not attack if the creatures around it attack. if you attack it, it will take your shape (not exactly), but be naked and weaponless. At a certain point in it's health it will turn into a nix hound and attempt to run away. if you give chase and bring down its health further it will turn into a bird. If you manage to kill it after that then you get extremely valuable and useful powder.
Snotlings: They will run and play in the ascadian isles. If they see you they will hide away, but if you manage to kill one you can dig out a valuable "heart stone" from their bodies. Not a very potent ingredient and pretty heavy, but worth the weight.
Haunt: A ghost that can only be killed with silver arrows. only found at night around tombs, but will vanish at the first sight of humans. The Haunt carries a magical essence that will teach the drinker a random spell or fetch a fair price at the market.
Lost and Foundone thing I think this game lacks is an incentive to go out and explore the wilderness. This would be a series of quests where a person from a town lost a ring or a walking stick on their travels. They will tell you this in a little secret or their initial greeting and it would not be an official quest. Other then completion there would be no incentive to actually return the item, but generally they would not be very good. Though ones that were owned by higher level NPCs would be in tougher locations and, as result, more powerful. Something along the lines of >something missing? "What? Well, I did happen to drop a ring of mine when coming back from my trip to Vivec, but it was a gaudy thing. given to me by an old friend, but really, I've been trying to get rid of it for years! It must have been when I had taken a rest under a tall ash tree right before I passed the turn to Pelagiad. Anyhow, do you need anything else?" and then the ring would be found on the ground under a tree before the turn. Just to add an incentive to travel or something to look out for on the road.
White Knights/Black KnightsTwo new orders have spread from Cyrodil: The Order of the Dragon and the Order of the Serpent. Just something that would add secret meeting places to the houses of nobles(white knights, dragons) and probably more nobles walking around in ceramic (low level, but pretty cool looking) armor and old rusty swords, as well as the black knights (serpents) who are actually serious knights, but are easily bought and not loyal to much, but the Order of the Serpent. The knights will take often be found taking stands at mountain passes. They will challenge you to a duel, otherwise you must forfeit all your money (since there is no way to actually get them to no be able to pass).
Sand Viper and the DukeDeath threats are being sent to the Duke and he has put his chief detective on the case. While searching out the popular Balmora tavern, the Eight Plates, for clues and suspects as to the identity of the "sand viper", he comes across an intrepid adventurer who is able to solve a riddle that had been stumping the detective for months. "What has a mouth that cannot be filled and no amount of water can quench its thirst?" (sort of a stupid riddle, but meh), the answer, of course, being a river. This leads the detective and the adventurer to explore to the south, near the mouth of the Odai, where a cave is found... (and that's all I came up with)