In theory Wasm could be supported, but generally JS/TS is much more efficient when running inside isolates (our lightweight sandboxes) since you don't have to bundle a language runtime into the app. CFOS at present only exposes JS (with TS coming soon).
Please add Wasm support :)
I'm making a whole new language to get around the problem you're talking about: it brings no runtime at all. One of my targets is a Sandstorm like system I've been slowly working on, but I'd love for it to be a fit for the actual Sandstorm successor.