Note: If you're just skimming, try to read the first sentence or two of each point to get a vague summary of each suggestion.
Suggestions:
1) Many concepts of Darkfall are cool (
YouTube - Darkfall is coming). At the rate they're going (apparently they've been working for 6+ years), you could probably implement a clone game in a year or two and beat them to production ;-)
2) VR is the future. Be the ones to bring it to MMO's (even if it's in a limited form due to current crappy networks and hardware). Make it compatable with keyboard/mouse (though limited). Of course all VR equipment would be USB or other standard PC plug (and you could probably make decent money just on the equipment sales).
3) Base it on an existing book (though you'd probably have to get permission). This would give you a small increase in player base of the fans of the book and would only have you write a small bridge of storyline. For Sci FI, Dune by Frank Herbert is popular and hasn't been done in an MMO :-P Another option would be the Otherland series by Tad Williams (which would be kind of funny because part of the story line is being trapped in a VR world and having to go through different areas). As for fantasy, another medieval setting would be Tad William's Memory, Sorrow, and Thorn series (humans, and other races).
4) Regardless of what you do, a point that Darkfall emphasizes is freedom to do what you want. I think this has helped prolong the life of UO, and would make a game playable for the next 10+ years if there was enough freedom.
5) A unique idea that hasn't been put in an MMO that I know of yet is death. Permanent death. If a player dies, that's it. Time to make a new character. The Otherland book depicts a VR game that has it. Deaths are "reviewable" to make sure it wasn't a game glitch that caused the death. This would add an entirely new aspect to how you organize your play in the game.
6) Closely related to point 5, Characters could also have a certain lifespan (based on their race?). Of course, I would think it would be "extremely" long (five real life years? or some crazy number of play time). This would add the effect of having veteran players not get too bored because they will eventually die and need to make a new character. You could add the aspect of "wills" and graves (also for point 5) so that you could retain all or part of your posessions, and also leave your mark on the world. Players would compete who could be the oldest character on the server. If you used play time, this would inhibit people form just sitting idle while logged in, and/or macroing on their main.