In a properly rigged weight mapped clothing set, helper bones are simply not necessary. At all.

In this set, there are no helper bones and no additional JCMs (except what are in the original figure and transferred to the cloth) and only one morph to move the left side cloth up in a crouched position so that it does not intersect the ankle.

The thigh bones BECOME ghost bones in this rig and can be moved as the user sees fit.