Welp the J30 is a base of $6,000 and is less than yours in what it offers but has a good following.
A very similar prodcut is the Gazel/ American Safari. When Mat at OE was trying to get these to offer he was about $15k. Now that Red River is offering them they are at a base of $18k the last time I looked. It's a little more than the J30 in offerings but 3x the price. Even given the 15" extension I think they have out priced their product if you consider what a final all in cost would be. I was a buyer of this unit when Mat was trying to sell them but the price bump and poor customer service shut that down with RR
The Earth Roamer was/is a very similar product and if I remember right pricey too. If I recall they only sold something like only 10-15 units.
IF you could get a quality product out, in a timely manner, have decent customer service, and stay as close to $20k as you can I think you stand a chance to carve out a niche.
That said, you can add me on the mailing list when you start one
ratled