If sanity were to become āhidden,ā then maybe that one trait that lets you see your exact health could also detect sanity levels, or perhaps a different trait just for that.
I suspect that the psychopath trait would matter in at least some cases. If nothing else, you wonāt get sanity loss from killing and corpses.
Speaking of corpses, there should probably be some sort of limit for seeing them, so that it doesnāt become too overwhelming after a battle field; One corpse looms just like another. If nothing else, for balancing reasons.
There could possibly be a trait called āsensitive mentalityā or something like that, which makes you go insane a lot faster.
Maybe certain pills could help you with your sanity levels too.
(Oof, this was longer than I expected)