Hi Peter,
it's possible to get rid of all the language file and all the help files you don't want but there is some effort before success:
I got LiberKey as well on my HD as on my USB drive.
1. Delete all language/help files of every program manually!
A hard job but necessary!
2. When you deleted all unwanted stuff copy your whole LiberKey folder to your USB drive.
3. Whenever a program is updated I never update it on my USB drive but on my HD!
4. Then I compare both installations with FreeFileSync to show all the differences.
The differences are the updated program files and the pack of language/help files in the unwanted languages which come by default with the update (only on my HD).
5. In FreeFileSync I choose which files on my USB drive get updated and which files on my HD get deleted.
So I get after every update very quick rid of the unwanted files and both my HD and my USB drive got only the files I want even when my USB drive has less files installed.
It's really simple.
Be blessed, not stressed.
Cole