I would say that the burden of proof is on me to prove that Binary AST is a significant real-world performance win and that it will not cause undue burden on JS engine implementors.

I don't think the "burden of proof" philosophy requires me to disprove every other possible approach, right?

I explained my reasoning for my statements in the comment itself. If you believe WASM could address this use case better, and are so inclined to build a toy proof-of-concept JS-to-WASM compiler, I'd be very interested in seeing it.