As a side note, the Archdemon Wings are my favorite wings ever. Not a whole lot of servers have them but I'm pretty happy they're here.
GMs could always make a light and dark version of all the wings. Then make versions of the later wing stats for all the wing appearances. That way you could have whatever wing style you want with the same stats. It's mostly a bunch of copy pasta work and making an NPC that could work it. That solves the wing problem and adds more customization at the same time.
Then if the sides still aren't balancing out, change the system up more.
Ths text is a signature placeholder: Not quite as creative as a signature 'could' be. But probably more creative than yours.