While a nice idea, it would be worth finding out why github abandoned this very concept in favor of gemcutter.org before diving in head first. I trust the github guys as being far more competent than most in all matters of distributed source control especially when it comes to package management.
The idea is sound, but it was a distraction for us, so we were more than happy to offload rubygems to a dedicated service that could give it the attention it deserves.
