I'm not sure the best way to word this...
You aren't thinking outside the box.
Don't think about it as putting a spin on current/traditional MMOs.
That's what lots of games do(Tera, Guild Wars 2, Defiance, etc...) an end up stopping short of innovation.
Think about it as building something new.

For example.
Most MMO encounters are based on scripts that are pretty straight forward. Do A and B will happen.
Utilizing more advanced AI could make fights truly dynamic.
So it's not about mastering a fight by rehearsing it/watching it 700 times. It's about mastering your own character to deal with whatever is thrown at you.

It's impossible both logistically and economically
Nope. Not sure that you know what impossible means.

There are games being released this year that are innovating and producing truly dynamic multiplayer content. It just hasn't transitioned yet because WoW is still the safe mold as far as MMOs are concerned.
It may take a couple of years and it may not be my exact vision but things are moving in that direction.