I personally wouldn't mind this IF it's like a transfer student which you are allowed to reject entry to the school.
There's plenty of people with the mindset "Looks female enough" so it's a good addition for those people.
Branching plots of that sort are a terrible idea for a game that's already this big. The only way to do it is to basically have the added character be a complete nothingburger who never participates in anything, due to the need for writing different scenarios. The content drip is already slow enough without troubles like that. We also already have a lot of added characters that have 0 content, like the athlete girls, and the unseen trouble girl, who I'm not certain if you can actually deny entry. Oh and Arabella also has nothing going on, despite her mother having loads of content.
The best way to get this sort of action in the game is the Headmaster visiting that boy's school we sometimes hear about. or their Headmistress visiting our campus with an aide.
Also, people getting upset about homosexuality in their media that already features plenty of lesbianism are children who should get the Headmasters punishment, maybe they'd be normal afterwards.