Make sure the new tank is on the [VehicleTypes] list. If not on the list, the game thinks it doesn't exist, and throws out the unit code on game load. Once done you should get the 'Missing Cameo' at the very least. Give the unit Prerequisite=FACTORY and you will be able to build it as any side. (Make sure the unit has no ForbiddenHouses= or RequiredHouses= tags, at least for now). If the game crashes when you click on the cameo, or crashes when the unit is about to roll out of the factory, well those are other problems
