I have tried to make my own groups for the RHS factions but I can't quite get it to work. I have mostly made the groups smaller in size, moved them to the "correct" categories and lastly I deleted all Armored groups and made new one with some of the heavier mechanized units instead, so I could make them rarer.
However the M1A1 tanks still spawn even if they don't exist in any of the groups in my description.ext file, so I guess I'm doing something wrong. (when I open orbat at mission start I can see that all my groups gets loaded correctly though)
description.ext: https://gist.github.com/anonymous/f8dafd7493617793ee0ed08d8a92fabe