Hmm.
I really think a lot of people are getting carried away about the "optimal" society, if people were around only those in their quadra... I don't think everything would be happier.
To be honest, I think how things are right now is optimal. Surely everybody here has personal friendships with those outside their quadras, right? I have a pretty diverse group of friends myself. I think, considering each quadra values certain functions highly, we need to have a decent balance of every function.
Interacting and "getting along" with people unlike you, or who approach things completely differently, will forever be discomforting; but sometimes a little psychological discomfort can give you a new perspective, and help growth.
More practically, I think the marriage screening/typing could be useful, for important relationships, or maybe for choosing a company to work for, seeing the breakdown by % of what your coworkers would be.... but segregating entire societies?
More harm than good. We all need each other.