My vote would go to Mercury (shocking, I know), followed by Bling! or Anole. The team meant to publicly represent mutantkind really should feature more non-passing mutants, and either of these three would also add another queer member.
Mercury
Anole
Dust
Rockslide (the real deal)
Surge
Gentle
Armor
Hellion
Winddancer
Elixir
Bling!
Wallflower
Indra and Trance (as duo)
Pixie
Others like Onyxx, Tag, Rainboy, DJ, Cipher...
My vote would go to Mercury (shocking, I know), followed by Bling! or Anole. The team meant to publicly represent mutantkind really should feature more non-passing mutants, and either of these three would also add another queer member.