Could it be done this way that you copy PE/Brit and then replace them with RedArmy/Ostheer and then add PE/Brit as actually new factions - this way RedArmy and Ostheer should be able to recrew weapons and PE/Brit wouldn't? PE doesn't have any weapons to recrew anyway, and Brit only emplacements.
4 fully playable factions in game at any one time
Yeh, only 4 can fully work 100% (re-crew, automatch, ranking).Unless Relic changes something on their end.