As a follow up just because I’m still thinking about it. I had a long discussion with a friend about this one time and he advocated for a tiered approach. So instead of having a men’s league you would have an A, B, and C league and people are placed based on performance. If we go just based on pure athletic ability then the A league would be mostly men and the C league would be mostly women, but there would be upward mobility and likely a mixed league in the middle.

This might be a good model for younger kids, but by the time kids reach high school the biological gap is too great. See https://boysvswomen.com/#/ This is a problem because high school is the time when college scholarships become a thing, performance in competitive high school sports matters. Also, you now need three leagues instead of two, which could get expensive depending on the sport.