Thanks for your suggestions ....
about using MainDIctionary ... this can be change by the user in the working profile, so it doesn't reflect language pack in use
about LOCALROOTPREFIX, I've to check on that one, because when I install an English language pack on a french version of Autocad 2013, Autocad was still pointing to the french support files directory (ROAMABLEROOTPREFIX keeps its original value, whatever the starting language is), so I was getting English interface and commands at the prompt but french menu and ribbons, I'd to edit the support files path by changing the location of the support files... so more to come on that one as soon I can get an hold on the test PC.