world.Repop() is useful, but sometimes you might not want it to repopulate the entire world. For example, in a project I want to repopulate a z-level once all players have left it (so when someone comes back, it'll be repopulated). If I call world.Repop() when a z-level becomes vacant, it'll potentially cause a just-killed enemy on an occupied z-level to respawn. I'm sure other reasons exist for repopulating select regions of the world.

I'm not sure how it'd work. Maybe Repop() would take a list of turfs as an argument and it'd only repopulate objs/mobs that were in the specified list of turfs. If no list is given, it assumes the whole world.