Awesome! I'm going to have to try this out!
[edited]
I just realized why I think this is a great idea.
Many of the expansions I've seen seem to try to add flair and stuff to try to make the older systems appear to be a lot more than they are, at the expense of resources. Your approach seems to be more of; make it work really well without squandering the resources... not to mention it doesn't require trying to track down and overpay for 3.9.

Cheers!