To either make minors more powerfull and maybee free up majors industri to focus production on other stuff. IRL The swedes sold their Bofors AA 4cm and Sweitz their AA Oerlikon but that type of equipment might not be covered seperatly in the game. I know that hoi3 got license build but to see other nations want to use my nations stuff in their units could be awsome. That ofcource if the unit could have several types of equipment in their YOE. Like forexample Ge 1 Pz division got say 50 Pz Mk III h, 12 Pz Mk III j, 10 swedish pansar type 42 and some captured T34 at the same time.