Perhaps the question should be, why do you want to breed designer clownfish?
If your thinking of making a lot of money, I'd say your chances of that are remote. It's not unusual to have only a few really good fish out of a whole spawn.
Before you worry about any of the exotic varieties, set your self up for breeding them, and then breed a few generations of normal clowns. If you can do that, then you can try your hand at one of the designer types of clowns.
Be prepared to spend a lot of time and money on such a project.