make monkeys have lower stamina and overdose thresholds than people

[The Gorog]

How about a compromise. Make monkey arms a specific type of arm, similar to werewolf and space bear arms. And have the monkey arms just deal less damage or less stamina damage.

Not sure if you missed the post of this being about player-controlled monkeys of Berrik later on, but player and NPC controlled monkeys are usually using items to beat up players.
Unless the arm type also has an impact on the damage that melee weapons do, which I dont believe is the case currently, then this would only make a difference for the monkeys that come fresh out of the vendor and havent already grabbed the knife, toolbox or any tool thats often on the way to where you want to take them.