The idea of RTS game play being introduced into a MMO would be a pretty killer feature. But, let's be honest, that would be a HUGE undertaking and would take away from what needs to be focused upon...core game features and mechanics.
I think BioWare is experiencing that right now with SW:TOR. The character story aspect of that game is an AWESOME game feature, but there is too much of it with all the little zone quest. I think they easily could have dropped a quarter of the solo story line, and spent that time on balance issues, additional Flash Points, end game issues, etc.
Would I like to see something later on like that? Absolutely! Maybe Goblinworks, some third party dev, or a community member equipped with a tool kit could develop it after launch as a type of module add-on game pack.