I'm betting against wasm and going with containers instead.

I have warm pool of lightweight containers that can be reused between runs. And that's the crucial detail that makes or breaks it. The good news is that you can lock it down with seccomp while still allowing normal execution. This will give you 10-30ms starts with pre-compiled python packages inside container. Cold start is as fast as spinning new container 200-ish ms. If you run this setup close to your data, you can get fast access to your files which is huge for data related tasks.

But this is not suitable for type of deployment Cloudflare is doing. The question is whether you even want that global availability because you will trade it for performance. At the end of the day, they are trying to reuse their isolates infra which is very smart and opens doors to other wasm-based deployments.