I havent played it so often yet, because I am really not so good at it... :)
So I don´t know if this modifiers exists in any way already:
How about a modifier ("Grate-O-Mania") which doubles the amount of grated cheese which is coming out of the grater when you are cranking ? so the advantage would be that you are serving the customers faster (maybe you would have to extend the "perfect" range a little bit because someone would not be so exact when grating double speed)
(sorry for my bad english, I am german :) )