Cross with ranchu with wakin? To increase size of ranchu? I think may be a 10 year project ler at least, seeing that you need a few generations to fix any characteristic and considering you need at least nisai or oya fish to work with. Like body to look like ranchu, high percentage of fish with dorsal in spawn, etc.

I think one of my Thai ranchu and my black ranchu pair about 4 year mark now. Black ranchu first spawn offspring also about 2 year old mark now.