The right path seems to be a WebAssembly build of an actual C++ engine. That's pretty close to this, which uses ammo.js, a workerized emscripten/ASM.js build of Bullet.
I've been meaning to experiment with doing precisely this :/.
I've been meaning to experiment with doing precisely this :/.
About WebAssembly - it is a future of Ammo.js/AmmoNext. We are planning also to make AmmoNext modular with wasm modules.