So, I tried to run a 5e game using my own version of gritty rules, including 1e/2e overnight healing, slow HD recovery rates, use of HD for primary healing, and a modified exhaustion mechanic that still used 6 levels, but had graduated minuses that affected all classes (including spellcasters). I'll try to answer your OP based on what I experienced:- Firstly dropping to 0 hp doesn’t mean unconscious. It means a serious wound - a real medical emergency but not completely out. They still take death saves as normal but when on 0 hp characters can’t rise from prone but can take a single bonus action, a single action, or move (but not stand up). Taking any action or move forces them to make an additional death save.
- Secondly, I’ll be using the slow healing rules. Spending HD is the only way to regain wounds, which represent bandaging and rest. No spending 8 hours to wake fresh as a daisy.
- Thirdly, and this is the doozy, I want dropping to 0 hp to cause the Pc to gain 1d6 levels of exhaustion. Yes the PC has a 1/6 chance of dying instantly when dropped to 0 hp. When their head gets lopped off. The exhaustion represents their wound - which they are free to describe as they like. When their exhaustion is gone (through the normal means) their wound is gone.
1) zero hp and prone, with one "action": that would make it scary to be in that position, but you'd have to think through the possible "actions" that could be used: attack? spellcast? hide? The additional activity forcing another death save would require some thought on the part of the player, hopefully a cost/benefit analysis.
2) works for me. That's what I used, but it really didn't "slow down healing" very much in my campaign experience as all the players were some form of caster. It did slow down the pace of play, which was what I was going for, but wasn't really "slow" per se. And I also ascribe the one or two encounters in a day, sometimes long stretches without any.
3) Using the 1dnd exhaustion, this could be a big hit at 0hp. It would compound #1, due to every action or move being affected by the minuses in the exhaustion rules. I found in my game that avoiding exhaustion was the driving factor for my players, regardless of where they were with re: to HP. So they would hunker down and take awhile to rest to remove exhaustion (and remember, this was a granular system over 6 level, not standard 5e exhaustion). Now, of course, the scenarios/game/campaign I was running mostly allowed for this, but their slowing down also caused events to unfold that they couldn't then intercept in time.
I agree that the bounce up from zero/bag o' hit points/heal everything overnight is not what I want in a game. But I was also unsatisfied with how it all rolled out in my 5e game. Best bet is to just try it, and roll it back if it doesn't work.
We've been playing OSE lately (less hp, less busy rounds, quicker gameplay), and using Goblin Punch's Death and Dismemberment Table, which gives us enough of a feel of "you don't want to go below zero" balanced against dying instantly at zero, since it combines long term injuries with "fatal wounds" that work like death saves. That could probably be modded to work in 5e.