How ok... thanks !

Sadly, no. I tested checkpoints with a friend a while back, and the module to make soldiers friendly until you act up doesn't work and the soldiers will always shoot you. The rest of the module works though. If you have another way to make the checkpoint guards become hostile if you act up, you can use old man checkpoints with that. For the rest of the modules I have no idea.

old man modules compatible MP COOP ???