One day a lady footballer will emerge who is so good that she will need to play in the Premier league, in order to bow to the equality movement. And rightly so.
Imagine a footballer as good as Ronaldo, who happens to be female, being forever consigned to the Women's league. It wouldn't be fair or right. And there would be some kind of exception made allowing men's clubs to sign female players. And that would be the start.
But then it swings the other way. What about lower league male football players who are good enough to play in the women's Premier league? They would have to allow it to go both ways. There would be resistance at first but it would happen.
The inevitable outcome, after a few years of ifs and buts would be that any player good enough for the "mens" Premier league, regardless of gender, can play in that league. And the same the other way.
So it would just become a mixed competition. With the best players at the best teams and the worst players at the lower teams.
In the short term at least, it would mean a mostly mens top division, with a few exceptionally good women. With probably a few more women as you drop each tier. Then most of the lowest division and non league would be made up of the best women who are better than what would have been lower league men.