ToME WikiI actually implemented this idea way back in Angband 2.8.3 or so, but it's been ages since I hacked on a 'band, so I'm putting my suggestion here instead. Pretty simple - an option that, when on, causes all monsters of level 0 to not disturb you. This includes townspeople (urchins, mercenaries, and the like) and a couple of other creatures (the cat and dog). Of course this is a dangerous option to turn on when you're a level 1 mage, but it's very possible that a level 50 warrior won't have any good way to kill townspeople short of walking up to them and whacking them over the head, which makes navigating the town quite irritating. Why not let the player simply ignore enemies that are clearly no threat, if they so desire?
Incidentally, when I did implement this, it consisted of adding a new option, then making a one-line change in the disturbance code (basically changing "if the player sees a monster move" to "if the player sees a monster move and (option is not set or (option is set and monster is not level 0))". And the same for if the monster appears, too, of course.
-Derakon