I realize that the tank spawns as the same person every time he gets frustrated. It seems that if the tank is killed by a server command, the next z_spawn tank will go to him for some reason. pk_ and I have developed a workaround, but I'm having a hard time find enough people to test it with.
I'm posting the new plugin here because I haven't tested it yet. It'll show an error code if the randomizer fails, so if you want to help me out, go ahead and try it out. I'll try to test it on my own time.
The good news is I'm that much closer to making this campaign compatible.