JGarrettLieb has a point. MLS has proven itself very good at reacting to situations and altering the rules to prevent loophole abuse. If CFG try to find a way to accommodate Demichelis like this without making him a DP (and thus getting rid of one of the existing ones first) then simply put, they will fail. The salary cap, love it or hate it, is sacrosanct in this league.
Do you have a source for the coaching story? I simply can't see Yaya going into coaching. I don't think he has the right temperament for it. Honestly, I see Yaya as the kind of guy who doesn't want to stay in the game once he's hung up his playing boots. The most I see him doing is that Club Ambassador role that his agent talked about (which I'm pretty sure was just posturing, anyway, as I'm not even sure he'd be a good Ambassador).