It sounds like definitely an opportunity at the minimum for the existing online interviewing sites to provide a service which installs a candidate's vim configuration (or emacs, not sure how that one works) from a public Github (or other host) git repository URL. They've already gone through the trouble of sandboxing the runtimes somehow so it can't be that difficult to also sandbox the editor. Not sure how it would work for other IDEs but that should at least support vim, maybe others like VS Code and IntelliJ too.