[Loriel]

My suggestion for the engine would be to add a server option that defines callback functions in the Control-NPC that gets called for baddy deaths and removing vases and bushes and whatever in the level boards.

I cannot see a simple way to have a script detect when the board gets changed in such a way, and replacing all tile-based bushes with NPCs does not seem optimal either (while it sure might make sense for baddies). The Control-NPC seems like the right place to put this since changes to the board are pretty independent of any particularly player that might be involved. If that is too many Control-NPC triggers or something, another server option could define a probability for it to happen.