something that hasn’t been addressed is “stretchiness”, I can wear two pairs of fitting socks over each other because they stretch.
perhaps we could (eventually) have a size system for your character and clothing, each body part (or just you as a whole, which would make it simpler) would have a clothing size, when you refit a garment you could choose what size to make it, and stretch would allow a garment to go up [stretch] number of sizes. So:
my belly size = 6
my t-shirt size = 5, stretch = 1 (will fit)(layer 6 taken)
my t-shirt size = 5, stretch = 1 (will not fit)(layer already taken)
my jacket size = 7, stretch = 0 (will fit)(layer 7 taken)