For my house rules, I wanted to take inspiration from the 5th Edition exhaustion rules. I want, as a referee, to be able to tell a player that her or his character gets an exhaustion level and to be understood.
This is only a prototype, but I hope the Exhaustion Level and the Hit Points will interact in interesting ways.
After a combat, unless the referee judges it necessary, each surviving character takes an exhaustion level. Falling at 0 HP results in falling to Exhaustion Level 5. Reaching EL 6 means death.
To shake off exhaustion levels one has to take a rest (but be already at max HP).
Initially, I wanted to give the player the choice between gaining back HPs or shaking off an exhaustion level, but I renounced. It's interesting to give choice to players, but, well, a rest is a rest.
I introduce a wounded state, that slows down recuperation.
I need to polish the rest conditions, maybe factoring the quality of the camp/billet in the recuperation.
There is this optional rule where the post-combat exhaustion level increase may be avoided with a successful CON TC check (1d20 ≥ (21 - CON score)). That's adding a single roll at the end of a combat. Exhaustion Level maluses on check do apply to that check as well.
What is missing for now is a path between unconscious at Exhaustion Level 5 and death. How long can a character stay unconscious and crippled before dying?