Maybe to block out body skinning have a ui where can assign a number/color to selected faces. Then when done have some kind of script which can map the number/color to a joint. So suppose made the first pass of joints for body. Then tell script which number should go to which joint. Then hit a button and voila all the colors get blocked to the joint specified.
I can imagine there could be additional passes to smooth out verts between two joints so that the blocking isn't incredibly dramatic…
For a highly dense mesh, maybe something similar is to split mesh into pieces. And then have the pieces parented to joints. And maybe tool can duplicate all the mesh pieces but instead of parenting skin the pieces to joints and it figures out weights to set by using the parenting structure.
Inspired by David Brooks (linkedin dot com/in/dabrooks)