My Campaign Rules
In my campaign I've changed the rules a little more strongly, but not (I think) in a way that's broken.
A quick note about the campaign - magic is very low, and raising the dead is almost unheard of. So I needed to make death less likely. Also, in my experience, the 10 point range from fine to death has always been a bit too fine to me, especially the two point range from fine to unconscious. So I wanted something that "fixed" (to my mind) all these things.
Here's my rule:
* Between 0 hit points and a negative hit point total equal to character level, the character is reduced to one partial action move or equivalent per round.
* At a negative hit point total greater than the character’s character level, the character falls unconscious.
* If a negative hit point total exceeds the sum of a character’s level and constitution, the character dies.
So, a 5th level character with a 14 CON operates like this:
>0 HP - fine
0 HP - negative 4 HP - can still move/drink potion, but not fight/cast
neg 5 - neg 18 - unconscious and bleeding, 10% stabilize
neg 19 or worse - dead
It's worked great for us:
1. Increasing level and higher con are reflected as better survival chances, which I think they should be,
2. Even for a 1st level character with 9 CON it's as good (i.e., no more likely to kill people) as standard rules,
3. Lessens character death likelihood, and
4. Makes a "more realistic" zone of declining performance.
I should note, though, that enemies will sometimes use the coup de grace action if an opportunity presents itself..... and if you remember in real life, many combat deaths were indeed a result of the victorious armies walking around stabbing people who might have lived otherwise....
Over the last three years, we've come up with a number of house rules like this. If anybody wants a word file, let me know

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