This is basically what I've been debating.
As far as negative points, a penalty is a penalty, if you don't play, you get penalized. If you do play and support the queue, no penalty. This would fly under the proposed rating system, with the added effect of giving everyone the same opportunity from the start. Don't plan on playing? Don't worry about it. But the proposed penalty system would be pushing players who are active to continue playing, and not penalizing those who want to hang out until it gets rough once active players reach Gold and are penalized again with win/loss rating you get starting at Gold.
I do like your minimum requirement of games played, though. Regardless, it doesn't affect me because I'll get the rewards (minus the ugly crown) from the previous season and necklaces are poop. Not having new rewards gives no incentive, aside from new/old achievement titles. I just have to say my piece when people come in trying to "level" the playing field unfairly against the active PVP community.