Hey ! 3 years later I finally found the solution.
Like @Unnam8D, my mandalorian assault armor looked like in the screenshot from @darthbdaman's Mandalorian Armor Fixes mod. So I downloaded the mod to see the files and check if they were already in my override folder. And they were ! I think this mod was installed through the community patch or another mod. So first you will need to delete the files from this mod in the override folder. It will bring back the vanilla icons for the class 8 mandalorian armor and the class 9 mandalorian battle armor, along with bringing back the vanilla model for the mandalorian assault armor (the vanilla model being the classic mandalorian armor disguise).
Then you will need to delete the files from @JCarter426's mod. What I did was copy-pasting the option A files to the override folder and deleting them, then doing the same operation with the option B files. This way you can be sure that you've deleted all the files. Finally you can re-install the mod properly USING THE INSTALLER (this is very important, it didn't work properly for me when I simply copy-pasted the files into the override folder). Also if you want to change from option A to option B or vice-versa, keep in mind that you need to delete the files again in the override folder before running the installer again.
@JCarter426 Okay I used cheats to get the armor again and now it works. But I cant equip the yellow one (i can equip it if i choose option A though !). Do you know why ?
@JCarter426 Hey I've downloaded your mod but option B doesn't work properly. The icon show the full mandalorian armor but when Canderous equip it it still has the old skin. I've the Ultimate Character Overhaul mod but even with the compatibility patch it's doesn't change anything. Maybe it doesn't change the skin if I already looted it ?