I want to start a new game on hardcoe but without permanent companion death. Can anyone tell me how you change what hardcoe enables?

I could be wrong about part of this.

I know that the follower-unconsciousness death handling you get is tied to the "player teammate" status. That's not in question.

What I believe but am not 100% sure about is, that the hardcoe vs. not-hardcoe designation (follower dies vs. unconscious) is tagged in the .exe to work hand in hand with player teammate status on followers.

I've not seen anything in the followers' scripts which designates hardcoe differences in the death handling. It all seems to me to come straight out of the 'player teammate' status of the mob.