houserule on fighting fitness.

[dehro]

This may be an idea that's already used by a lot of people, but I'm not sure how and where to look for it, and I would like to know what your opinion is on my idea..
Spoiler: I haven't fleshed it out completely just yet... but this is the gist of it.

When a character reaches the last 10 % of their hitpoints during a fight, he can keep fighting but with at least a couple of points of exhaustion... I'm thinking 3 (but that's debatable). The idea being that if you've lost most of your hitpoints you're probably seriously wounded and unable to do half the stuff you'd do at peak form.
An idea to avoid this/mitigate it, would be to allow, at the beginning of the round, the player to roll a morale check, on his strongest stat, but at a disadvantage.
If he makes it he grits his teeth, rallies his last energies and can act normally for the rest of the round, if not, he loses the round completely.
It would be the player's choice whether to just take the disadvantages/exhaustion or try for a morale check.

Likewise, intelligent oppontents/enemies/monsters, would get the same treatment, with an option to surrender or flee, especially if they fail morale.

I'd have non intelligent monsters who reach their last 10% of hitpoints automatically fail morale, stop fighting and try to flee to the best of their ability... unless they were cornered, in which case they'd get the same exhaustion treatment.

EDIT FOR COMPLETENESS: the exhaustion would go away at the end of the encounter

opinions? variations? have you tried something similar in games you ran? how'd it go? is this going to screw over the players?