Mai would still have all those traits and still be a developed female character. He father problems could still be developed for "I wish I'd rather of had a son" and still had the same effect. And all the "I'm a guy hanging out with girls and it's weird" could just be summed up as "social awkward". And as for Mai's investigation in to his transformation is pretty moot as it's more about the fusion of grimoire and person that makes Mai a target and not so much the guy into girl aspect.
If it had started out like that, I probably wouldn't be so hard on Remix Heart. But now, it's just dumb plot points for the sake of being as PG-13 ecchi as possible.