I've seen similar topics like this brought up and I totally agree with it in order to implement it successfully we kind of need a a major change or more likely a complete overhaul of the current tag system.

Say I search for female Eevee's. The only way I can get guaranteed female Eevee's is if I throw in the solo tag. If I don't throw that in the Eevee could be any gender and just be with a female of any other species. This is the same problem that you have.

The new tag system would need to be crazy specific but I think it's possible, a lot of work, but possible.