> so nobody is happy and the law is followed.

An outcome so common they invented a word for it: https://en.wikipedia.org/wiki/Malicious_compliance

This would be a way better outcome than the current default. I've even seen this suggested before [1].

If game-specific logic is not public, information needed for reverse engineering could be completely missing, but if game-specific logic is available plus the names of the missing libraries, reconstruction of the game should be possible eventually.

[1] https://drewdevault.com/blog/Open-sourcing-video-games/ (See "What if I don’t completely own my game?")

Yes, partial source is still very useful. I don't think the law should allow for it though as companies could intentionally put as much as possible into "proprietary" libraries that they conveniently only license for binary distribution from a totally unrelated company that for no reason at all is owned by the same stakeholders. Much better to just require everything to be there and then have the industry adapt.

This is already common with source releases for games and it is much much much better than no source release at all. A lot of the proprietary middle ware ends up being not that hard to replace after all.