Not exactly sure of the process you are using to create the winpe environment, but what I had to do, as I just tried upgrading to WinPE4 for 7.1, was:
locate the winpe.wim file bootwiz uses to create the boot.wim file
- mount it using the DISM command
Dism /Mount-Wim /WimFile:C:\winpe_x86\ISO\sources\boot.wim /index:1 /MountDir:C:\winpe_x86\mount
- use another DISM command to add the packages I wanted...and their corresponding language packages
Dism /image:C:\winpe_x86\mount /Add-Package /PackagePath:"C:\Program Files\<version>\Tools\PETools\<architecture>\WinPE_FPs\winpe-wmi.cab"
and
Dism /image:C:\winpe_x86\mount /Add-Package /PackagePath:"C:\Program Files\<version>\Tools\PETools\<architecture>\WinPE_FPs\en-us\winpe-wmi_en-us.cab"
and then unmount and comitt
Dism /unmount-Wim /MountDir:C:\winpe_x86\mount /Commit
These commands are right out of the Help for WSIM.
Hope this helps.