Not quite a solution, because I disagree that the rights of accused and accuser are preserved by the school performing an investigation / making a decision.

In the theoretical that is true, but as a matter of practicality, such investigations / decisions usually interfere with the rights of the accused, accuser, or both. The most common example is that a university will force one or both to make a statement without a lawyer present, threatening disciplinary action (up to expulsion) if such a statement isn’t made. That directly interferes with a right that a person would have in a court of law because that statement can then be used in court.

So, yes, I think mandatory reporting of allegations is a good start, but I don’t think it alone solves a problem that exists with current Title IX enforcement.