Me and a friend have been waiting for a while now for mods to finally be usable in co-op.
I'm mostly talking about mods that modify the .pak files, as they are the vast majority.
Whenever we tried before, game would instantly crash whenever one of us tried joining the session with a modded .pak file, even if it was a identical file.
We went as far as uploading our .pak files so the other one can download and have the same exact file, but no cigar.

Without this I feel no desire coming back to the game, nor does he.