> A purely compiled WASM approach

I would love to see if a browser could like... "disaggregate" itself into WASM modules. E.g. why couldn't new JS standards be implemented in WASM and hot loaded into the browser itself from a trusted distributor when necessary?

Missing CSS Level 5 selectors? Browser goes and grabs the reference implementation from the W3C.

Low-level implementations could replace these for the browsers with the most demanding performance goals, but "everyone else" could benefit from at least remaining spec compatible?

(I guess this begs the question of "what's the API that these WASM modules all have to conform to" but I dunno, I find it an interesting thought.)

Yes, that would be a compelling change. Like a language agnostic HotJava platform. We're overdue for a more coherent approach, from the bottom up.