Rotating joints has been suggested before, but the previous ideas i found were clumsy, adding joints or joint states. So how about making the limbs rotate? as in, the forearm becomes some sort of joint whose state can be changed to rotate the wrist, biceps rotates the elbows and lower arms, thighs ==> lower legs, and shins ==> feet.

This would make movement damn near 100% realistic without changing current game mechanics, which means it can also be made optional fairly easily.
It could even be off by default.

Imagine all the BJJ possibilities.
A lil' sketch: