I fix it in
[RH] Faction: Allegiance
and
[RH] Faction: Coalition
so there will be 2 types of way with
C:\Games\Steam\steamapps\workshop\content\294100\2130877773
and
C:\Games\Steam\steamapps\workshop\content\294100\2130878466
folders, if you need make it only for one of it, check wich folder exist and make changes in it. I can't say wich exactly folder name used for mod.

1)
Need to change belt to Shell, it's written in the
https://steamhost.cn/steamcommunity_com/workshop/filedetails/discussion/2130877773/2797251919713505696/

but it was not enougth for me, so next steps help if you see probels with
asssaultBackpack

2)
Need to fix label name "asssault" to "assault", with 2 "s", not 3
example of my way were it placed
C:\Games\Steam\steamapps\workshop\content\294100\2130877773\Defs\ThingDefs_ApparelDefs\Apparel_Belts.xml (1 hit)
Line 9: <label>asssault pack Multicam</label>
C:\Games\Steam\steamapps\workshop\content\294100\2130878466\Defs\ThingDefs_ApparelDefs\Apparel_Belts.xml (1 hit)
Line 9: <label>asssault pack SURPAT</label>

After it it still not find texture, but it try to find correctly
3)
Need to make copy of existance textures to name starting with "AssaultBackpack"

!!! make copy and correct it, not change existance texture

Example:
SURPAT_AssaultBackpack_Fat_east
to
AssaultBackpack_Fat_east

it need to make with all backpack textures by way like
C:\Games\Steam\steamapps\workshop\content\294100\2130878466\Textures\Things\Apparel\Belt
C:\Games\Steam\steamapps\workshop\content\294100\2130877773\Textures\Things\Apparel\Belt