Stocking is more of an aesthetics/behavioral question for aquaponics. It's not like a fish tank. You have huge amounts of biomedia, and if your nitrates start to climb consistently, add more grow beds.
I agree 100%
hence my comment about the "Train Station" look of the Fancy Goldfish in the video link. If you go that route would will find they are very good little POOP factories.
You'll also find that larger excellent specimens will have some resale value.
In my home I just don't see the having space to raise table fish in a cost effective manner.
My Level II goal is a pond outdoors next year with grow beds. Fish will be cichlids. As I've raised them outdoors in the past.