Everybody who played games at some point spent some time thinking "If only this game had feature X from game A and feature Y from game B it would be the perfect game!". Obviously MMOs are not immune to that kind of thinking, in fact, Massively had a column called MMO Blender where the writers would describe their perfect MMOs if they could mix and match features from different existing games. This seemed like an interesting exercise in thought so I decided to create my own FrankenMMO too. I will be just sticking to the mechanical parts though because genre and setting are like ice cream, they are all good in their own ways. While mechanics it is much easier to discuss in an objective way and debate the merits and flaws of each one.
I will try to give examples of games that has the features I am talking about but I am pretty sure I am missing tons of examples. So keep that in mind, please.
Oh, and if anyone needed proof that I should not ever be put in charge of designing an MMO (or any game, actually) then this will be it. Unless someone wants to make the Titanic of MMOs, in that case I am your man! :p