Best case scenario, you have a bunch of females fearfully avoiding the male or vice verse, most likely with frequent spawning resulting in hundreds of young bettas. What are you going to do with them? There's always a strong chance that the females will gang up on the male or the male will pick off females. I don't understand why you would even want to do it. If you want a group of bettas, then get all females.
I'm even beginning to see sororities falling out of favor here. Eve if you have everything perfect, something can randomly go wrong one day and you can end up with one or multiple dead or injured fish. Bettas come from massive rice paddies where they have plenty of room to themselves. I don't think they were made to live in groups in close quarters. From what I understand, bettas in sororities tolerate each other at best. Not saying all sororities are bad, but an all-female tank is risky enough. Putting a male in there is 100% asking for trouble.
And now these three remain: faith, hope and love. But the greatest of these is love. - 1 Corinthians 13:13