You think so? Sounds like an awful idea to me that would restrict opportunities for women to play at the top level, as men on average are going to be quicker, stronger, taller etc.
I'd say the sport is a lot more physical than you're suggesting. If we separate in tennis I can't see how we'd combine in football.
I also think it would be tough for a male player to give their all against a female opponent.
I like the idea of football clubs treating both first teams as first class citizens as has been suggested above.