It has come up before, although the instance is gone and I suspect it only lives on in the Internet Archive. I generally stand by the points I make there - different instances could work for people into different things and federation would allow people to adjust their settings to fling out a wider net. So I might be on a regional instance but want to throw my net wider to include furries or uniform dating or sugar daddies or feet. However, you'd need quite a few people signed up to make an instance viable but that also might be where federation comes in, although that might not help if you are a lonely guy in Tokyo looking for a girl who likes cats and the only other person around is someone in Belgium who is looking for a guy who will dress up in an inflatable unicorn outfit.
I also thought that the approach in this study could be useful.