I think the answer is all head shots get penalties in games (like for high sticking). Make them double minors, if there is injury 5 and a game.
Then they should suspend based on number of prior offense and not how injured the player was (eg 1st time is 1 game, 2nd is 2 etc).
The headshot prior history can come into play if there is a different offense (eg boarding, knee on knee) but those aren’t used for head shot priors (except maybe boardings since those can be head injuries).
Somehow the real inconsistency seems to lie more in which hits get reviews and phone calls than what the actual consequence is.
Also, in case of suspected head shot I would like to see them real time reviewable. College hockey does this with head shots.
I just think a stricter on ice in the game catching and punishing head shots will make more of a difference than this whole spin the wheel of Justice post game crap.