I decided to look at weight painting again. I've looked at improved weight paintings before, but never ended up reusing them. So I have written a little Blender plugin that saves the weight painting of the active object to a json format text file. Given that you can already transfer a weight painting between two objects in Blender this is no big deal, but I plan to build it into my mhx2 exporter/importer so that I can automatically replace the default painting with my favorite painting.
I repainted the left shoulder of a toon and created a video showing the default painting on the left and the new painting on the right as the shoulder is abducted:
https://www.youtube.com/watch?v=CJ3RZJnTYs0
I used the corrective smooth modifier for both shoulders. While far from perfect the new painting looks better in pretty much any position. While I don't think you can achieve perfection just with weight painting I expect that someone with more experience can do better so if anyone has done a good weight painting it would be great if you could share it. It would certainly speed up my project!
If I can put together a good weight painting I'll make a stab at figuring out how to get MakeHuman to use it.