The error that you are running into and the solution seems a little odd. I don't normally setup the drives in my answer files since I don't want a live disk that can wipe out any machine without a safety stop. There is a screen that appears during installation that lets you partition and format the disks prior to install. I am asking to test to see if by chance the problem is related to the disk setup in the answer file.
My book covers some of the details on UWF and Shell Launcher setup: https://annabooks.com/Book_SGWin10IoTE.html. I have developed some utilities based on the WMI API sets to help with setup for Shell Launcher and Keyboard filter: https://annabooks.com/Software.html. The Shell Launcher command line utility can be called with a Pass 7 command to setup Shell Launcher.
Understood about going from WES7 to Windows 10. As you are finding there are some differences between WES7 and Windows 10 IoT Enterprise settings. Make sure to take a closer look at the power setting to see if there are any additional items for your platform.