I like the concept of a trans character, and there definitely needs to be more properly represented trans/lgbt characters in games, but I feel Ukulele is likely to play this element a bit safe - maybe a single, non-major NPC who gets a throwaway line?
Banjo Tooie had Jolly Roger and Merry Maggie, clearly not a conventional couple, but the portrayal of Maggie was somewhat... Demeaning, perhaps? If they include a trans character in Ukulele it should probably be an understated mention rather than the main heroes.
(And for the sake of argument, I happen to be transgender. Let the flame wars commence!)
Came to save my sister, stayed for the quiz show.