I really hope ESO becomes a successful MMO and stays true to Elders Scrolls experience. With that said, here are my suggestions to the development team at Zenimax:
1.) World Bosses & Legendary Items: The developers should add world bosses to the game that have a chance to drop legendary items (e.g. Daedric Artifacts). These outdoor bosses are extremely rare and spawn at a random location. When a boss spawns, there is a zone-wide warning. To defeat, you require a well organized 12 man team. Imagine visiting a small town when all of a sudden you hear bone chilling laughter. You look off in the distance and see a powerful Lich roaming the countryside.
2.) Darkness is important for ESO: The developers really need to make nighttime and dungeons dark. Now I'm not talking about making it pitch black. People need to appreciate torches and spells like magelight.
3.) Dueling & Inspecting: The developers need to add dueling to the game. Dueling allows players to get accustomed to PvPing and helps them practice for the Alliance War. This may even help get the die-hard PvE players out of their comfort zone and help with the war effort. For those players not interested in dueling, have the option to auto-decline any such request. Lastly, a player should be able to inspect another player’s equipment.
4.) Character Sheet Background Story: The developers should consider allowing players to add a background story to their character sheet. Basically, a small text box would be displayed when other players look at your character sheet by inspecting (works with item 3). This allows you to feel more connected with your character, which ultimately increases immersion. People could write several basic facts about their character, or even write a background story. This feature is for the role-players.
5.) Unarmed Skill Line: The developers should add Unarmed Skill Line (Martial Arts Skill Line) to the game. These skills would be based upon stuns/disarming opponents as damage will be low. This would be a welcome addition.
6.) Craft Cloaks: I’m hoping the developers add the ability to craft cloaks with varying styles and quality (cheap burlap to fine linen). Would be epic to show off your guild colors and/or symbols with your new cloak!
7.) Rested Experience: The developers should add “rested experience” to the game, which slightly increases experience gained from exploration, killing mobs and completing quests temporally. You get the rested experience when you log-off from an inn and it slowly accumulates when you are away from the game. This gives casual gamers an extra incentive to log-in and play. Basically, it's a good customer satisfaction mechanism.
8.) Instanced Dungeons: I think it’s very important for instanced dungeons in ESO, places where I can go and play solo. A good MMO finds a balance between solo and group content. I do not want to see random people in dungeons with me. If I want to do a dungeon with friends, I can invite them. The experience is ruined when everything is dead and/or looted! Maybe the perfect solution is letting the player decide how to run the dungeon, instanced or public.
9.) Character Origin & Birthsign: At the character creation screen, players will pick their Origin and Birthsign for their new character. This is for flavor only and does not affect gameplay. To pick Origin, players will choose from a list of home cities (based on chosen race). To pick Birthsign, players will choose from a list of constellations under which that character was born. Both Origin and Birthsign will be displayed on the character screen. Again, this is to add flavor to your character. http://elderscrolls.wikia.com/wiki/Birthsign
10.) Tamriel Holidays: I’m hoping the developers add holidays according to the Tamriel Calendar. This adds a fun element to the game and makes the world feel alive. http://elderscrolls.wikia.com/wiki/Category:Holidays