Hi Stjepan,
If Kornel's GSoC proposal ends up being geared towards extending ggl 3D functionality (which I think would be great), perhaps you and Bruno Lalande could serve as co-mentors for the project? I think something similar was done in the past with Mariano Gabriel Consoni working on Jeremy Pack's Extension / Reflection library - the official Boost mentor was Hartmut Kaiser but Jeremy was also involved in some capacity.
You had the same idea as me and Barend, and like you I think it would be great. Unfortunately we had a private discussion with Kornel about that, and it seems that the idea of working by extending our library (or Luke's one or Brandon's one) doesn't really seduce him. It would have been a pleasure for us to help him in that task. However we couldn't be the official mentors anyway since we're not the authors of an already accepted Boost library. Bruno