This is how I manually handle #372 until there is a better solution in Rollup internals.

This is great, thank you! Even works in --watch mode 🤘

Here's a pattern some may wish to use to leverage this feature to produce minified bundles without duplicating config:

import uglify from 'rollup-plugin-uglify'
import { minify } from 'uglify-es'
const activeConfigs = [ /* array of rollup config objects */ ]
const minifiedConfigs = activeConfigs.reduce(
  (minifiedConfigs, activeConfig) => minifiedConfigs.concat(
    Object.assign({}, activeConfig, {
      plugins: [uglify({}, minify), ...activeConfig.plugins],
      dest: activeConfig.dest.replace('js', 'min.js')
    })
  ),
  []
)
export default activeConfigs.concat(minifiedConfigs)

Assumes activeConfigs define a plugin array.

And here's what it looks like in the context of a production module without Babel.

What should we do if we want to build a bunch of assets in parallel but we want to host 1 webserver that contains multiple landing pages that are artifacts of the parallel builds?

Should I just configure ONE of the parallel builds with the webserver? Will livereload be triggered across parallel builds?