If you're just going to kill everyone, I think you should be forced to wear the collar for the rest of the game.
*chin scratch* Should certainly be harder to remove, but if they're gonna make it so you keep it they'd have to have dialog and stuff where NPCs react to the fact that you're wearing it still I think <- Probably easier to just have an alternative side quest where one removes it themselves. A really hard side quest thats mandatory given that you placed yourself there, even.
Nothin' wrong with a little genocide and mayhem, but consequences should be enacted story wise in some manner, hopefully
