I think it would be pretty cool to have some multiplayer aspects. For example a trading tavern system where people could auction (oh God, I know I'll get some adverse responses to my use of that word) items or something like that.
Also I think a multi-player mail system would be pretty cool. Sending fellow Tamriel explorers updates on what you've found, a new potion you've discovered, etc.
Me and a close friend both play as immersively (no quest markers, role play in perk choices, etc.) as possible and both find that chatting after about what we discovered is a nice immersive way to get some help (as opposed to writing on forums, looking up guides, etc.) Why not talk to your fellow travellers and see what they've learned?
Could you imagine an in-game forum system? haha. Head to the College of Winterhold and check the tome of knowledge to see what fellow mages have discovered, etc.
I think it could work.
