Now if only Chromium could learn to write WARC archives, then it would be on par! :) Great project!
I've been thinking along those very same lines for a long time (this project makes me wish for more free time). I have half a mind to fork this and add something like https://github.com/internetarchive/warcprox , or at the very least walk through the generated HTML and brute-force inline all assets as a first pass :)
This must happen either in the browser or in a proxy like the linked warcprox, in order to catch everything. But the proxy solution is getting less practical every day with key pinning and HSTS.
Maybe a future firefox will have an option to export everything to WARC?