Suggestion for organizing the collection is that you could organize the characters by the season they were introduced.
IE: Separate sections for BFDI, BFDIA, BFB, and TPOT.
I actually have several BFDI characters but they're easily findable elsewhere. I dunno how much they really count but there are these really weird BFDI characters that are technically spriteswaps but stupid broken, and found on a Japanese site of all things:
https://u10.getuploader.com/mugenup/index/date/desc/2