Try to copy your file(s) in the "WORK -> INTEGRATE -> UPDATES -> x86 -> Updates" folder or "WORK -> INTEGRATE -> UPDATES -> x64 -> Updates" folder (it depends on your ISO architecture).
Because WinReducer uses DISM to slipstream all Windows Updates, so both "*.msu" and "*.cab" files are supported.
Just DO NOT REMOVE in WinReducer for your first try :
- "Accessories - Help and Support"
- All Languages in WinReducer
Then in a 2nd try remove "Help and support" and all unneeded "Languages".
Please let me know if it works, because I will integrate a new option to integrate language packs !