My first idea is to be able to repair upgraded armors like metal armor mk2, combat leather jacket with regular metal armors, leather jackets.
Since they use the same materials and components i dont see why could not use pieces of one to repair another one.
And my second idea is to be able to repair armors with regular crafting materials, like repairing a metal armor with metal parts in wich case every metal part can give 10% of armor condition and an extra from repair skill.
This could be done with leather jackets/fibers,geckopelts,brahmin hides, metal armors/metal parts, alloys and even combat armors/hq metal parts,hq alloys
Have fun, Kalo.