Ahahah! Even that woman's side isn't gonna turn people away for something like that. Well, things have changed after all. Anyway, neither side has "limited slots."

When you graduate is up to the higher-ups to decide, but the process isn't too difficult. You get an offer, you take it. Get a wish, receive power. Refuse and you become one of the "good faithful"~ Or you fail, and you become one of the faceless.

I don't know what Exael told you, but choosing "Heaven" doesn't give you much at all.