After delving into this, it seems Wasmer tried, but as they weren't standards compliant, adoption/ecosystem support never followed.

The Bytecode alliance is taking their time stabilizing wasi. wasip2 which is needed for the wasi-http realm this relies on has only really existed for a few months as a stable Rust target, and still misses a lot of the really cool features that will come with wasip3 like full async support.

I suspect Cloud providers will adopt wasi after 1.0, but that is likely years away. I don't think wasi-http will change much before then so now is the time to start building with it.