That was my original thought, and the reason the master is a double shrink. At one time I thought of flipping the working pattern to cast iron and then still be able to cast a dead nuts 1/3 scale in aluminum. But that was also ten years ago.I would think loads of people would pay a grand for this casting kit just so they could build the engine and see it run.
The main stumbling block is the hand work to core the block, manifold and heads. I spent a year of my spare time developing the cores and getting a good head casting. After all that and knowing every thing that is required it takes me 16 hrs to get the cores for two heads mounted on their bases. Then by the time they are shaken out and cleaned up enough to start machining, another 8 hrs. has been spent. So, not counting fuel and supplies, at a barely surviving shop rate of $50/hr that is $1200 for a pair of heads that require a skilled machinist with the proper tools to finish and match them to the block which itself takes about the same time as a head, and then the manifold, also about the time as one head. Then the water pump, oil pump, pistons, vibration damper, all castings and the fan, valve covers and pan sheet steel blows the cost out of the market.
That is why I did the little single
I thought I could match plate the crankcase and send it out to a jobshop foundry, and do the same in cast iron for the cylinder. The rest is either purchased or made from bar stock. Bringing kit cost below $300 opens a large market and could work, but I'm doing other things now while I'm still young .
PS I added a couple links to your thread "So now you can....." last night.