Thank you! Looking for and trying to get uncommon but awesome oddities is one of my favourite things to do in this hobby. So its a pleasure to help you.
Acquiring some of these fish can be very difficult and requite a lot of patience (like several years). But not all.
Before I continue, I forgot to mention the Japanese white spot pigmy filefish (Rudarius ercodes available tank bred).
All suggestions I made are suitable for a 50 gallon tank. I have or have kept all suggested genuses. Most also in my previous 55 gallon tank.
Split fin anthias are very difficult to get hold off. You will need a good relation with a good shop. A shop where you can put a special order in and that is open to really make an effort for you. They will need to continuously pester their wholesalers to get them in. If you can, find a shop that transships or imports them selves, they have a more complete insight into stocklists at exporters and may be able to put the request in with them directly.
Regal damsels (Neopomacentrus cyanomos) are being tank bred by Biota and ORA. Biota has named them N. azysron on their website, but that is wrong.
https://www.algaebarn.com/shop/captive-bred/fish/damsels/ora-regal-demoiselle/https://shop.thebiotagroup.com/products/lyretail-damselfishGetting them wild caught is less of a problem than with the split fins, but still requires special ordering.