Bob, I can only speak for myself and I have to say I only have a basic understanding of why a phono cable needs to be designed differently. Assuming phono cables do need a different design (I'm using Morrow phono cables today and they sound good to me, but ....) I would be interested in what you would bring to market given that you seem to be providing better performance for the money elsewhere.
I like how you explain why you design your power cords the way you do for example on your web site. That makes sense to me. Your speaker cable design is again, compelling.
Getting back to your question, I would need RCA connections for my gear, but I understand many could use the din connector at the turntable also. Perhaps that is another cable type where options might be needed.