Thank you for getting in touch! While we recognize why this kind of story might be of interest to the people who would participate in an exchange like Rule 63 (many participants who offer/request Always a 63 are excited about exploring how a character's life could have been different if they were a different sex assigned at birth), it would not be a story about a character having a different gender than their canon one, so it's out of scope and wouldn't be possible with our nomination format. We do have an existing "you can offer/request a story about a canon trans character magically getting the physical body they want" exception to this, but that's more about making sure that our rules are set up to handle the "wacky magical change" fandom usage of genderswap in the case of characters who are already trans in canon.

Edit: Or art, mods forgot about art again, sorry.