Up Vector Trick (Update)
So in the HERMES auto rigger there are a few areas where a joint chain is used to drive an another joint chain using an ikHandle. This can cause issues when the driver chain is straightened because now the "knee" joint which is the pole vector target is now on top of the joint whose orientations it is supposed to control.
In the past I have solved this by parenting a locator to the knee joint and offsetting it slightly so the locator could never wind up on top of the ik "knee" joint (which was the cause of the unstable pole vector). While this is stable in all the cases I have used the rig in, it could be better.
So I tried using a technique to extract the axis of the joints in the form of a vector. It wound up working perfectly. It doesn't effect speed because both methods are very light weight, but it does get rid of some clutter in the outliner.