Ed the Bat wrote:"Wonky"? I'm genuinely curious to know more, because this method you're using has its fair share of problems. For example, if a new monster is too big to fit, the spawn fails. Also, if the monster being replaced is supposed to have a TID, the new monster will not. Both of these things have broken maps while I was trying to play.
It's a bit of a moot point, seeing how I'm probably not going to go through with it now, but back when I was working on the Mush... the game kept crashing with a fatal error when I had added it's randomspawner and booted up the game with -nomonsters. (Although admittedly it was probably something else doing it), and changing to that system seemed to fix it, so I just used that system for every monster.