OK, just one more idea.
@kripken just reminded me that one of the early ways we can promote Rust on the web is the exact same way we promote Rust for other software stacks - write a high-performance module in Rust and call it from JS. This plays to our strengths for all the usual reasons, doesn't require solving DOM bindings. And we've got quite a few crates these days that are approaching world-class performance for their domains.
I have several high-priority tasks on my plate still for the immediate future, but I hope I can turn the corner on those and pitch in technically myself.