I've thought of creating not one ghost per fire, but one ghost for each force per fire. If any force has bots nearby, they would drop the canisters on their own blueprint (the entities would have to have a zero-collision box, obviously), and on removing the fire, I'd remove all remaining entity-ghosts. Would that work, or would the ghost on top block the other ghosts for good? It's hard to test this, so if anybody already has tried something like that, it could save me some time.
