Constraint Symmetry

Adds constraints to the selected side so it mimics the location and rotation of their opposite bone pair while keeping their individual roll values intact (Which means animations will not break), removing the need to do double the work when armature reproportioning. After the desired position of the armature is done, clicking on the apply button will convert that pose onto the resting pose and remove all constraints.

Parameters

Symmetry Offset

The position and rotation constraint of the selected side is absolute, which means that it'll mimic the position and rotation of the other side regardless of its resting position, which can be very noticeable in armatures that are not completely symmetrical. If that is not the intended result, toggling Symmetry Offset fixes that by making the position relative to its resting position.

Opposite Arm Rotation Fix

Very few armatures for some reason have wrong roll values on the UpperArm bone causing said bone to rotate in the wrong direction which certainly isn't the intended result, Opposite Arm Rotation Fix fixes that by inverting X,Z instead of X,Y in the rotation constraint.

Notes

This function does not work with Team Fortress 2 armatures, so it's disabled for said armature type.