I would like to see a new version of the GEM layer based on Open GL.
Rationale: The old Garnet port paid for by Apple uses a lot of Traps and other features of the interface which are likely to break when Digitool comes out with the MacOS X native version of MCL (currently in beta).
Porting to Open GL seems the best way to get out of that trap. It also might give a big leg up on making a Windows compatable Garnet interface.
I've taken a look at the project, and it looks doable but rather large.