Just throwing this out there: Surprise set. You get 4 random pieces from different sets in 1 package. Maybe there could be a tier1, tier 2, tier3. Like, tier1 would include cheaper/less popular sets in it's pool, and so on. It's not exactly what your main idea is but I think that would create for more diverse options as far as mix-and-match apparels go.
I'm not really for separating by piece because of the cons leba listed above(too much work, less revenue), even if it saves players some rum. You can't really ask anyone to put in work and sell for cheaper. It's like saying, "I'll buy the supplies for my deck from you but you gotta build it for me." (I worked at a lumber yard, sorry.)
At best you can have a "black market apparel" sort of deal for each type of piece.