If the Bynars got their shit together, do you think they could join, invest themselves in the landscape, and then outvote the rest of the old school collective who might not be happy with the opinions of the new majority?
I imagine the Federation told the Bynars to breed. Just go to town on each other, outlaw contraception and then start mass cloning samples of Bynar's by the continent to...
The Borg wouldn't be stupid enough to assimilate something as terminally virile as that just becuase they're so dead sexy?
It's not like the Borg are %98 ego.