Oscar, I agree with the spirit of what you are saying and the process that you are laying out. I also like your idea about mentorship a lot.
A key issue to understand when handing out commit rights is that the person who gets commit rights doesn't necessarily need to be very senior. Most important is that the person respects our cvs commit guidelines, understands his own level, and is humble and communicates with the community. I would rather give commit rights to a beginner programmer with all those traits than to the best programmer in the world who doesn't respect our guidelines, can't see things from others point of view and won't compromise.
So far I don't know of any evidence of substantial harm caused by giving out commit rights. On the other hand though, I can give you numerous examples of great code improvements that have not found their way into the toolkit.
