Pretty cool. Do you have a list of features you plan to support and plan to cut? Also, how much does this differ from the DOM impls that test frameworks use? I recall Jest or someone sporting such a feature.
WASM support is not there yet but it's on the roadmap and we had it in our mind since the beginning of the project, and have made our dev choices accordingly.
So yes it could be used in a serverless platform like Cloudflare workers. Our startup time is a huge advantage here (20ms vs 600ms for Chrome headless in our local tests).
Regarding v8 in Cloudflare workers I think we can not used directly, ie. we still need to embed a JS engine in the wasm module.