These are very cool additions! I'll have to think about how they'd fit into the mod as it currently stands...
One more thing that may need doing in that modification, if a monster death is required to trigger something to enable advancement. To be safe I should probably make sure that code like the last few lines of monster_death_use gets invoked for all the ghosts (and then maybe NOT do that part of monster_death_use when it actually dies). Will get back to poking around at that soon.
Edit: E4M7 is a nice test case (the vores at the end). Made a couple of changes so that that map is completable.
Edit 2: Checked that all maps are completable.