Hi
Second version is ready. Some changes are made:
https://github.com/black-punkduck/MakeHuman-HelpersI added two directories blender2_7 and blender2_8 .. I changed the name (sorry) to io_mhw_import_export.py. Take the correct version for your blender version and throw away the old one. I will support the 2.79 for a while because I still have some trouble with 2.8 here and there.
The new one is able to import and assign the weights as long as you use the same geometry (in your case the proxy).
Sometimes I added vertex groups and then did a new group, like one for hair or e.g. no_volume for a double use of the armature. Now try to smooth the groups
Either the hair is shorter or the no_volume is not no_volume any longer and the bones are only doing half the work. Or I corrected a knee on one side and need the same on the other side. That's what I am working on at the moment and most is ready to go now.
At least I can now replace the groups assigned with new ones. Also my old characters can get the new proxy-weights without loosing other groups.
For the symmetry I do an export of a .mhw file, pipe it through symmetrize_weights and import it again. This also works on additional groups. The only thing you need is a mirror_table and so I improved the function create_mirror_tab.py also. A mirror-table will allow you to find the vertices on a non-symmetric character (which normally is every character exported from mhx2 btw). This table is useful for everything. Weighting, adding shape keys etc. The table should be created from proxy.obj directly. But even this geometry was not 100% symmetric ... so it is a good idea to have such a function. The table will contain -1 for all non-found vertices.
In one version I changed a few manually to get a table.
Using a mirror-table you can also use this table to create a 100% symmetric wavefront.obj (symmetrize_geom.py).
In the end most of the tools will be available inside the blender plugin as well (or different ones, I am not 100% sure).
The scripts I did are mostly used on CLI now, because for debugging the tools I work on CLI.