Wow. This has been a long and wild ride. But you and I made it together. We now have the full recipe to automatically configure a Microsoft BI demo machine with PowerShell. Of course there is more to be done, such as configuring other Service Accounts and deploying demo content; this script however saves me a lot of time every time I need to stand up a new demo machine.
You can download the script on Github. Please note (again) that the code is provided as-is and you should use it at your own risk. It is probably still buggy but should give you a good starting point to adapt it to your needs.
I enjoyed the ride with you; hope I made your life a bit easier of the course of this series. Enjoy!