That idea has legs. It's the first time I see the concept here; have you or Barbara written about this before?  

Except that the "modern world" has a knowledge base and a technological infrastructure which allows you to do things that would be impossible from the Amish starting point.

Well, otherwise it wouldn't be possible to "upgrade" an Amish community! I agree that the technological infrastructure is something off a cheat; it would need rethinking. (How do the Amish get their asphalt anyway?)