I have now worked around the problem by creating a new progression.xml file for all Izayo weapon packs (5.56, 7.62, 9mm, Shotgun, 45acp and 30.06) and placing it in a folder called zzz-CustomMod at the end of all mods.
Then I moved the progression.xml of the individual mods to a backup folder.
Now all mods work together with those of the other authors and all weapons can be made at the workbench.
As a further benefit, I have added the file so that the progression is now visible in relation to the weapon skills, a small detail that was missing from the original.
Here is the link to my file, feel free to use everything I have customized in it, your weapon mods are great
https://mega.nz/file/KioUUbDA#uC9hyQs84ukdUuxDDPaiZ8SBWc24HqWhQgyf2g_w-sw ---> V2, messed up some entries