With the Windows 10 in-place upgrade task sequence, you can't do a custom wim, that I would normally do to capture all the latest patches. I'm curious to how others are dealing with this. Are you putting in a command line at the end to run wusa.exe and install the .msu file for the latest cumulative update?
Currently the Install Updates ran at the end takes far too long. Probably because it needs an update to the Windows Update agent itself.