The issue in ADK 1703 is that you cannot mount a WIM file in MDT/ConfigMgr, due to a signing issue with the WIM Mount Driver when running a system with UEFI and Secure Boot.

Workaround:

Michael Niehaus did found a workaround today, and that is to use the existing WIM mount driver that is already in the system.

https://blogs.technet.microsoft.com/mniehaus/2017/05/16/quick-workaround-for-adk-1703-issue/

/mike