I've always wanted to do something like this, but it comes down to enough volume to make money.
Died in the wool car guys have lots of options, so whatever it is has to be "fantastic" enough to keep them from the other options, but as a percentage of sales I don't know how much of the kit/replica market they make up (perhaps FFR has data, but would they share it?)
Second, it seems to me that whatever shape is settled upon must be unique enough that it's not easily found and known broadly beyond the car culture, because it expands your potential market, and said market segment probably generates enough sales to push profitability.
The bathtub Porches were well known, and especially Cobra's and street rods. Originals for all of those are not easily found, expensive beyond what most are willing to pay, and the base parts easily found (air cooled VW and Ford V8 parts), and everybody knows what they are, even if they couldn't pin down the exact year of any of them were produced.
The miata is probably an excellent mechanical starting point, and I'm sure others could be found, but beyond an XKE, I'm not sure there are too many sports cars that carry the recognition.
An Elan probably looks too much like a Miata to the casual observer, the Alfa is probably not unique enough to be known outside enthusiast circles. A 510 gets you closer, but then who besides a car nut wants one?
It's a tough nut to crack. I think the racing series helps market to car/racing types, and might boost sales a little bit, and too, it depends on the cost structure and sales price per unit, but I think there's a reason most successful replica manufacturers have been the three already mentioned.
Buzz kill, I know, but I really would love to see more variety in the market, especially for the small bore stuff that I have an affinity for.