Fictivite has posted about wanting to use more stealth and knocking out opponents in games and included a system to enable doing this that will fit many old school games on the Fictive Fantasies blog. The system works well for not only players, but also for monsters. This is quite a big thing as many games that I’ve experienced (from both sides of the screen) tend to devolve into killfests rather than attempts to subdue and restrain opponents. In part, this is because many games have killing damage as the default, and then complicates things by adding subdual damage which requires tracking another set of numbers on top of normal hit points lost so that you determine if someone dies or is knocked out. Some games do provide rules for knocking creatures straight out (such as the classic rules for subduing dragons!) but often those are highly unrealistic.
I tend to use subdual damage, with 25% of the damage being real damage (applied first) and 75% going to a secondary track of damage. I keep track of the whole damage taken, and cumulative subdual, as per most rules, and depending upon what damage takes a character to 0 or below, that’s either a kill or unconscious state. It works well for me, but does require players nominating that they’re doing subdual damage though.
I wonder if things can be better served, at least for players, by simply trying some simple rule changes. One possibility is if a killing blow is landed with a non-sharp weapon or the side of a bladed weapon, that ends up being stun damage and knockout if the hit points go below 0. Another is to flip is so that the default is that all characters are go unconscious rather than die unless a player states that they’re being killed (unless you do massive damage). Another option is to allow “tagging” of characters for unconsciousness instead of death and allow any player to determine that and having the group all agree to it; when opponents are unconscious then you can coup de gras and kill if needed without any further mechanic.
The other thing about flipping states from kill/unconscious to unconscious/stun is that it changes the feel and flavor of the game, and players stop being murder hobos. Plus, the complications of a downed foe getting back up later and coming after the players is always a fun thing to add to a game.