Now that you've laid the groundwork, I'm hopeful Pietta or one of the other repro manufacturers will offer this commercially. They could probably sell them for $2,000.
Personally I don't see a commercial market for it.
Uberti already makes a Remington Carbine with an 18 inch barrel.
And Pietta already makes at least 2 models with a 12 inch barrel that a butt stock can be added to.
I'm not sure that Pietta has the capacity to make another product, and with that expensive price tag.
And for whatever reason,they can't even seem to make more Star or Paterson revolvers that are in demand.
The only other carbine that I remember being produced was the Colt Root Model 1855 rifle by Palmetto.
For a variety of reasons it wasn't very successful.
Perhaps if it had been better quality it could have been.
I'll bet that some people would love those too, but not if it cost $2000.
Especially when compared to the cost of an Uberti Remington Carbine at $549.
If any company could make another Rogers & Spencer, and beat Pedersoli by doing it, then that could become one of the biggest new selling products.
But they sit idle and aren't attempting to make any of them for years now.