I don't think a JVM like chromium engine would really solve the problem. Most JVM end user applications ship their own JVM. By shipping your own JVM one can avoid compatibility problems and most importantly the user doesn't has to install the JVM which makes for better UX. The same would apply for Electron.

The only way I think a common runtime could work is if Electron used the Runtime of the Browser. If every browser exposed an API to run JavaScript and Render HTMl using the browser's Engine that'd be great.