That would be mighty awesome. Thanks for fast responding :)
Not gonna lie, I attempted to play Doom 3 in coop (courtesy of dehwm3 port and librecoop mod) and it turns out the progress wasn't saved whatsoever. The progress was kept as long as players were connected (going naturally from level to level carried the inventory).
As soon as someone disconnected - poof. All weapons, items, health, armour were gone. This was the reason why we had to drop the idea. If FCAV will allow coop players to keep their inventories for each checkpoint individually this would be monumental.