This idea was bouncing around my head earlier, but in a slightly different format - summoning shadow clones of various monsters to have them use their powers to aid the character. Something like a cross between a Binder, Shadowcaster, and Summoner. But that they could never be more than shadows, and so their effects were always weak/short/crippled, and that as the class/system progressed, what the character gained instead was more of them, more shadows that could act on his behalf, do his bidding.