[@Double] I’d imagine so. I’d like to think there are 3rd party or customizable parts in universe. However I think there would be certain restrictions. Like any gunpla that is painted with anti beam coatings can’t use Phase Shift Armor. I think to make it fair the paint is effective but less effective then nanolaminate paint that Post Disaster gunpla get. 

Also since the paint is it’s own thing it’d probably bring up maintenance costs.