I think this should be a common workflow..
to set a random color for each submesh, and then use this same color to create a color mask per color should be a one button thing ,Withouth any use or installing of any external tool by part of a artist oriented user.
For udim workflow I don't know a better way than working with color mask and blend nodes.
I'm working on doing this for myself, is very painfull to set up by hand each time, also the submesh coloring interface is very small, is very slow to be scrolling across each group and check if All the colors are different, and after that to be creating each color mask and sampling the colors, and then connecting blend nodes.. very very painfull and totally scriptable.
Can this be added as a feature request or at least submit the hability of the python sdk to write Color tables randomly by picking equidistante points on hues scale or something similar. ?
I'm working on recursion trees to generate this structures and generate the tool by requesting the color table by the part of the user, I'll be posting on the show case when it's done... but the better ways is just to write the color tables directly on the baking map proprierties, and to include all the baking setups on the python sdk would be even better, so I can match the same data on any further use along the material construction.