Actually, I believe you can already run webpack-dev-server with a multi-config just by making your webpack.config.js export an array instead of a single object. The article seems unaware of this capability, but you should be able to have both builds be part of a single webpack config file.
See https://github.com/webpack/webpack-dev-server/blob/master/ex... for a simple example. I've used this before for web worker scripts (which require a different environment than the DOM) alongside a normal build.