No doubt due to some abuse of mine (developing C-games that crash the simulator), my simulator can get in state where it is unresponsive, just won't die and won't properly restart. In this case it will keep bouncing in the Dock as if it is trying to start.
That's an odd one. The Sim isn't doing anything too magical, I'm not sure why macOS wouldn't be able to kill it/restart it. Have you tried killing it from Activity Monitor?
That is very odd (and not being caused by us). When it gets into the hung state, is there a Simulator process listed in Activity Monitor? If yes, can you Sample it and attach the sample?