We would love to do that, but...
Female MC is not difficult to add because of the story reasons. It's just that such a decision would require to redraw the whole game. We can't just simply make a girl MC and still use male MC H-scenes. And with the amount of content our game has, we just don't see any possible way to make such a drastic change in the near future.
Though that doesn't mean we're never going to do it. Just that currently we need to make sure the game at least decently works with one MC!