I guess it depends on the fate of the Xenor, Holy Grail is going through some revisions, although there is a probability they will be moved over to the new Garden World or not, not quite sure.
@Archetype Zero Oz is right, and of course, your idea is possible for the fact that this setting is not "ours" so to speak, in that such a human sub-species is indeed possible.
@Archetype Zero Oraculum Is correct, a sub-species is indeed possible, and as he also said, you'll need to discuss with the player who made the species.
So have you thought about which world to begin on? We of course have Terra, Joord and additionally we have other worlds that are open for one more species, such as Itium, Erelvath and Holy Grail's yet to be named Garden World. Plenty of options to choose from provided if any player is open to the idea(we know the former first two are).