attract people to higher mp levels dont force them...
and any new restrictions or what not bigger than they are now are forcing, and forcing could be unproductive..
EDIT: if u look at the daily statistics on the login screen ull see that the number of players that jump to mp4 every day is usually 1 to 3, and why they dont last till mp5 i dont know, but im sure its not because strong mp3's scare them away.
and mp3's should be able to train same creats as everybody else without any restrictions because if u restrict them with low level creats or decreased xp cap everything u will get is even weaker players with poor creats that will not stand any chance when they move to a higher level where players have better creats, stats and everything. maybe increasing xp cap for mp3 would be good so they have more space to train and test what works the best for them and to be ready to defend when they jump to higher level...