Hi! I’m the developer of CoopFoundry, a co-op mod for Captain of Industry 0.8.7 that now has a dedicated server.
Gameplay++ mostly works in co-op, but there is one real cause of desyncs. Settings changed in its panels (warehouses, market, bridges, parkings) go through a local request queue and are applied only on the machine of the player who changed them. The other machines keep the old values. A smaller point: a few parts run on Unity frame time, such as the excavator parking doors and the steam heater animations.
Would you be open to sharing the source, or to routing those setting changes through the game’s command system? That way they would reach every player at the same simulation step. I’d gladly send you the changes for review.
Thanks!