The limb idea reminds me a little of "Die by the Sword"
or the movie "Monty Python and The Holy Grail" :hero:
Maybe your idea can be implemented using total-body scales like:
pain, blood loss and broken bones %,
in addition to specific limb scales: attached (yes/no), movability% (broken%), pain%, infection%, where 100% = need to remove limb or to risk death.
My favorite combat mode in QFG was in QFG5 - choice of weapons,
fighting with keyboard so that each key present a different move (but using the mouse as an alternative control gives very limited movement to those that use it),
however I think there should be more moves - ability to kick and to hit sideways with elbows even when holding a sword, to spin while on ground to knock an enemy over,
all this in order to enable fighting against multiple enemies at once using keyboard with both hands (to combine moving, attacks, defences and magic/throwing things).
A good option could be to use the q...e to z...c keys (for limb movements) in combination with the numpad (for moving around in field) in order to get more control over movements + other keys for throwing things/casting.
Personally I disliked the combat mode in QFG3 the most and think the strategy in QFG4 took the fun out of fighting. What I really hate is fighting in turns (one move at a time).
One game that I think had great fights was "One Must Fall: 2097", except for the keycombos that are annoying.