"would Betty Blue Eyes have any real selling point in the US? It barely did in the UK"
It's novel and it's British.
American tourists love theme park musicals. What's more fun than a mechanical pig running around stage?
American tourists love British stories. Why else does every PBS station continually run Judi Dench and Patricia Routledge reruns? Americans love Downton Abbey. Americans love stories of cockney British pulling through in hard times. Look at the success of Call The Midwife.
Cast it with Victoria Clark and Eric McCormack and the tourists will come to see it.
If anyone ever tells you that you put too much Parmesan cheese on your pasta, stop talking to them. You don't need that kind of negativity in your life.