You just made my point for me with all those examples you posted. If you want to make this you breed that X that there's a goal in mind with those breedings. Breeding for ugly gray fish with long faces and nothing special is pointless when the pure species used are better fish in every way.
People crossed fish to make flowerhorns because they wanted to create colorful fish with big nuchal humps. Then they wanted pearls, wrap fins, shortbodies, so they added blood and did what they could to refine and fix traits. It's totally different. Think it through.