Maybe this has been mentioned already, but: Given we don't have any accounts of the blue istari that necessarily determine what form they took in ME (My opinion is that both their names and the descriptions of the Istari over all (as somewhat elder Men) could as well have been given by ppl who exclusively know Radagast, Saruman and Gandalf. (Also, Men could also refer to them simply looking mannish, not elvish or dwarvish) So I feel like casting the two blue wizards not necessarily as two men is not even explicitely canon-divergent, really.
(This is totally not in service of my Makar and Méassë conspiracy theory no sir xD) No, but kidding aside, I think this is a case where i wouldnt even speak of genderbending more than "not defaulting to male in absence of text that says otherwise"
And since this is a thread of inclusion of queer characters, i ofc could also see a blue istari with a not traditionally binary gender presentation as well, however they would present themselves in our world. Also to the discussion about relationships: It would be an option too to have a recognisably queer person that isn't instantly coupled up, especially if that person is a maia and has maybe set themselves clear boundaries on that subject.