I know its been mentioned a bunch of times, but I think giving a TO resistance to certain monsters would make the game a lot more interesting. Used to play Hengband a lot and having teleport other fail added a lot of excotment Imo. Wasn't a sure thing so you would have to try it against sleeping enemies, make sure yore health was high, or lure monsters from vaults and use other ways to deal with ood foes. Granted some classes had access to one of my favorite spells swap position witch was a really fun way to strategically fight.