Yeah, SlimGems may work for now with our RG maven patching since it is just a fork, but over time I am worried. What we really need is for RubyGems to accept some patches to allow us to hook Maven support in. Right now is probably a bad time to bring it up to them.
To date the issues with allowing uninstalling (or just plain removing) RG is:
1. 1.9 ships RG and we support 1.9 compatibility
2. Maven support is monkey-patching RG to work. If you uninstall and replace then this feature is very likely to just be broken.
Anything else? It seems this is getting dangerously close to WONTFIX (at least until the RG landscape changes to re-evaluate the idea).