It's funny, I stumbled on a similar use for iframes a few years ago that I did put into production. I needed to have a rather large SPA for employees hosted locally - that is, on a server on a local network in retail stores, not accessible from the web or unless you're on the same network as the server. The employee had to be able to load it on a tablet (but wouldn't necessarily know the server's local, dynamically allocated IP address without checking). And it had to be deployable without any complicated local DNS setups, router changes, etc.

I solved it by writing a discovery service... a wrapper that's accessible on a public (non-SSL) web page that basically opens a pile of hidden iframes and uses them to war dial local IP addresses until it finds the app and replaces the page's content with the winning frame's. Amazingly this janky thing has held up ;)

Anyway, nice work, and a cool idea!