I feel like Hedwig is a bit more complex than a cisgender male playing a trans female. To me, the whole point of H&TAI is that Hedwig struggles with her (it’s the pronoun used in the film, so I’ll use it here) gender identity - she was a cisgender gay male who agreed (barely) to have her penis removed so that she could marry her boyfriend and leave her oppressive country. Had that situation not arisen, I feel like Hansel would have been happy to continue to live as Hansel. To me, it would be irresponsible to have a trans woman playing this role. It seems like Hedwig tries to embrace her circumstances, rather than ever having actively wanting to go down that road. Full disclosure: I’m a cis female so my interpretation of this is simply that - my interpretation.