I have split out from the default dev container a separate WASI container to help make the default container image smaller. Both are now configured as a development containers in the .devcontainer directory in the repo. Both are also set up as prebuilds to make getting going easier. I have a PR for the devguide that covers all of this.
The key thing is working on WASI is about as easy as I think I can make it and I tried to update everything for general development as well along the way. Hopefully this has made it all easier to get beginners going at sprints.