Would that even work? seems like players always find a way to relate non-level games into levels. TSW claims that it has no character levels, but it does have item quality levels. So people will say need these classes for this dungeon must have QL3 gear and so on. Marvel Heroes has this thing where you hit level cap and you gain omega points. I heard that people were saying you need XXXX amount of omega points if you want to get in on this hard more raid. Even if you dont add numbers to them and make them purely "options" in name. I see people going we need a mage for this dungeon must have option A, B, C and D and customization X, Y and Z. And they ask for that because thats the minimum that people think the dungeon needs or whatever.
Anyways my answer to your question though is to forget about themepark MMO's. I want to see some sandbox MMO's again. And not based on some shitty background that i wont know about unless i read some obscure fan-fic book. I would like to see Star Trek, Star Wars, hell maybe even a Warcraft, Diablo or Starcraft sandbox.