This came about because I saw a mutant hound playing with a teddy bear right before my grenade blew it up, and felt so guilty that I had to reload.
Description from original mod: (credit: phantombs)
My additions:
Extend above changes to mutant hounds
(optional) set all dogs as "Essential" so they can't be killed
Note: Some quests require fully clearing locations (including killing all enemy dogs). If you run into problems with these quests, switch to the non-immortal version of this mod.