I like the sound of this, but I'm stuck on:
"Are we OK with serving noscript desktop users what is essentially the mobile version of our site, small images and all?"
Mobile-only? No. There are media selectors for device widths.
Interesting! Thanks for pointing out screen-size media selectors.
Given how on top of CSS quirksmode usually is, I wonder if there is some problem with using screen-size media selectors on mobile devices.