At this point it really wouldn't be much of a team-up. I'd just re-implement the better features of GV in SC - if it is even possible, I have to look at the code for a more specific comment on that. Then it would be up to Vinka to decide what, how, when it goes into release.
Vinka thought about my request regarding source-code and denied it... for now. He first wants to implement the features I mentioned by himself, because he feels that he can do so faster.
However, he also offered to send me the code for review, once he had done what he can do easily.
He also mentioned that he will abandon his multistage code and contribute it to fred18's project, because the features he was already implementing for a new version of his DLL were done by MS2015, too.
For SC4 he has some plans for the future, so he doesn't want it to become open-sourced. However, he wrote that he will make sure that the community receives the code if he stop development.
With this - and in light of the hopes, ideas and requests here - I'd like to invite interested users to post their input either on vinka's thread at Dan's or alternatively email him directly with feature requests, so he can take them into account. They don't make much sense here anymore, because Vinka also pointed out that he don't spend his time on Orbiter forums, except for a little at Dan's.