Hostile conflict angels don’t appear on the Astral Plane any longer, but all angelic and human beings are now immune to conflict on the Astral Plane.

Itinerant merchants who, if chatted with, offer one of several non-renewable trades. Generate on stairs, path to the opposite stairs, and once they reach them they disappear forever from the game. Generated with the requisite inventory to make all their trades. Always peaceful. Tougher than shopkeepers, since they have to defend themselves out in the dungeon. If you kill one, no more will ever spawn.

When polyselfed to foocubi of the appropriate gender, #monstering will seduce (i.e. de-robe) @ monsters.

Ankh-Morpork levels in the Tourist quest should be populated with some peaceful humans, dwarves and trolls. However, the levels should also then avoid having lots of narrow corridors so it’s not incredibly frustrating to traverse them. (Or implement peaceful displacement).

Bards as a monster, who spawn in a group of same-race monsters with a (sometimes but not usually) magical instrument, and they keep their distance and play songs to buff their allies.

Add a dogcatcher, who will come and impound your pet if it misbehaves (stealing from shops, killing Minetown citizens) and you don’t get it leashed before a certain amount of time has passed.