In a big planted greenhouse type situation with lots of hiding places you could keep a big mixed sex group. Space and hiding places is the key, and the ability to separated males off if they are being too obnoxious during the breeding season. This lady has lots of good natural quail keeping information on her website: https://holistic-hen.blogspot.co.nz/
Yes, providing you have 4 hens per male, 3 at the absolute minimum. I've currently got 4 groups - 18, 8, 5 and 6, with 5 males between them. Roughly 3.5 hens per male, and at present, all living peacefully. Long term they will hopefully all be living together, I'm in the process of introducing the 5 to the 8 and then they'll be introduced to the 18. The 6 are young still and will be introduced once they're fully grown. Enrichment makes a big difference - initially I had 9 and when breeding season came around, started to have problems with the two roos I had at the time. So I added cardboard tunnels and more branches, and a corner litter tray (sand bath) and arranged everything so that everyone could get out of sight of each other if needed. The aggression dropped right down. What was crucial was that nothing was put in a corner - no nest boxes with only one entrance, the litter tray is sat about 4" from the walls and so on. That way, there's always an exit route if one bird is picking on another. It's working well so far but I will have to add more stuff when I get all the groups together I think as I've not had more than two roos together so far.
