I recently answered a similar question and before that I asked it on StackOverflow. In the end, I made a demo for the solution I ended up using. https://github.com/workmanw/ember-multi-app. We use this pattern in production and it works quite well.
** Disclaimer. Ember-CLI does not officially provide support for this. It’s possible future Ember-CLI changes could break this pattern. Etc, etc, etc. Use at your own risk.