Hi,
I think it's really a good idea to use the local language pack from the site you're connecting to, allowing to have personnalised strings.
But it should be done only for the local changes (not the whole original language pack), keeping downloading the language pack from AMOS (or have in in the app), to be sure to have the latest version (for the case of sites where the language pack has not been updated for a while).
Séverin