So I went back and look at the elements I put in and didn't like the idea so I'm going to give you all an idea of what these changes are.
1: One for All can't give the user the ability to use the quirks from allies but I can still increase the allies quirks still.
2: U.A. isn't a school in the rewrite it's Japan's Department of Heroics because I don't think a lot of people especially kids want to thing about school when they want to unwind and watch TV.
3: So with the second point U.A. does work a bit differently because it allows you to join at 15 and if you pass an exam watch over by seasoned heroes.
4. Mr. Limitless would have given One for All to the top ranked examinee that year if he didn't meet and trained Airi.
5. Mr. Limitless' real name has been changed from Charles to Lucas
More will happen with this hypothetical rewrite in the future so keep that in mind.