I think surplus is a good idea done bad.
Why not do like Dissidia let the player choose what kind of gamer he is lets say this for example.]

Casual> The player get a bonus on SP/EXP for some hours thats intended to casual player after that SP get a big restriction that way it can fool the system.

Hardcore> The Player dont get restricted on the amount of SP/EXP he gets at all

I believe that way Casual player can keep up and Hardcore player dont get hold back, dunno if you think its a good idea hit up like if i get a lot i may put a petition for it