I guess it wouldn't harm to share the workflow, since there are no replies...
1. Move the character into the problem pose.
2. Duplicate the geometry to be corrected (A). Duplicate it again (B).
3. Sculpt and correct (A) until the desired shape.
4. Apply both (A) and (B) as blendshapes to the original geometry. I find that using the "front of chain" option yield the best results. Then set the weight of (A) to be 1 and the weight of (B) be -1.
5. Move the character back to the neutral/bind pose. You should see your geometry having some wierd deformations. This is perfectly normal.
6. Duplicate the geometry again (C). Delete the previous blendshape created, and both (A) and (B) can be deleted too.
7. Apply (C) as a blendshape to the original geometry. Done! This will be the corrective blendshape you require, which can be driven via set-driven keys or using the poseReaders plugin by Michael Comet.
The script still need some cleaning up due to some workflow issues. I'll try to put it up ASAP.
Next on the To Do list:
1. Muscle rigging. Attempt to setup a full muscle rig using Judd Simantov's free cgmuscle plugin. Aim is to understand the full muscle anatomy of the human body and attach them to the correct positions.
2. Revamp my auto-rigging script. The first version was done quite some time ago, which ever since then I've been using it in production without much time to further improve on it. There are lots I've planned to improve on, so I'll definitely do this somehow.