"The problem I am used to in Poser is that morphs get applied before the pose, so that any fix to the arm made while the arm is down won't correspond to the fix needed to be applied to the up/zero position arm prior to appling the pose. I want to fix the pose in ZBrush and convert it to a morph. This will require transforming all of the deltas from the local surface coordinates of the posed mesh to the local surface coordinates of the default pose mesh, to the best of my understanding."

The Poser MorphBrush uses a custom channel that applies the morph before the joint deformations.

You can also move a morph manually in the cr2 to be applied that way.