The optional facing rules aren't exactly the pinnacle of balance either-in every game I've played with them combat becomes a conga line of death. Also enemies respond to stuff like the rogue attacking them from behind out of stealth by turning around and focusing on the rogue.
Ideally, your system would account for how many enemies are attacking a creature, and allow them to face one enemy for free. If another one attacks from the back, they have to choose to turn their back on the first guy, which should have a penalty-an AOO is ideal. This is somewhat hard to implement in the tabletop, but relatively easy in a system like BG3.
