At my Grandma's times, if you bought a shirt it would come with an extra collar and extra sleeve cuffs. This is because those are the parts that get ruined faster, so you could change them instead of buying a full new shirt.
A lot of garments have parts that get worn out faster. The idea would be to apply the Grandma's principle but with a twist: the modular parts do not only serve the need to extend the item lifetime, but also come in different shapes and Stiles to give the piece a re-fashion.
There would also be the need of studying the technical aspect of how to make the substitution of a part easy and convenient, since there are not many people in modern society that would know where to start in changing a shirt collar in the traditional way!