I’ve rewritten and renamed Rigify for MB-Lab [Addon for an Addon].
There are still issues with backwards bending knees in some poses/animations with pole_vector = 0.
A proper layout for different bones (muscle, helper, MCH, etc.) to Rigify layers is a mission feature for now.
Please report bugs only in the Rigify for MB-Lab thread or on github (https://github.com/danielenger/Rigify-for-MB-Lab).