Trying a new rig once again. The shoulders are troublesome, even with three helper bones. I wonder whether I should rather add a muscle system, which would create more realistic deformations of the skin.

This test is a reather extreme pose; with arms crossed there are normally so many flesh masses compressed and moved by collision. I didn't add any collision deformer which is why the hands happily cut into the arms. The rig, naturally, doesn't help with deformations by itself.

To apply the rig, I had to make some loop cuts in the arms. That doesn't sit well with the morphs for the face. I guess I will need to program some kind of transfer of morphs from one point set to another. D'oh!

Given the number of manual corrections or (currently missing) automatisms, I doubt any animation that I'll do will ever show crossed arms.