As you will change language of system, system will revalidate all products and will check if any of the products is missing Name/Description, as per newly selected language.
If there will be any such case, of missing Product Name/Description, system will throw you one warning for each such product. The message of warning will be as under
"Text translations in ThisLanguage are not available for the products listed below. It is highly recommended that you provide the translations in order to avoid blank product names and descriptions. Select a product and click Language > Translations to enter the translations."
You can validate, above theory by looking at following path
AOT\Data Dictionary\Tables\SystemParameters\Methods\validateSystemLanguageIdChange
In my personal opinion, user having language FR, should enter translation/description of Product manually, each time, as he/she creates a product; since AX allows you to enter Product Translations in any languages, so it will be just one time entry, and from next time, as he/she will open ax, it will show them Correct FR translations.
In fact system is behaving like gentleman, as of now, in your scenario.
Lets suppose, system directly enters translation in FR language, (after you change language of system), what will happen next??? an EN-US user will complaint you same case.
again, in my personal opinion you may explain to user that its his/her responsibility to add translation of product in his/ her needed language. (user should do this after product is created, because at time of product creation system takes language of system parameters)
Note: if all of your organization is operating in FR language, you can change language from system parameters without any hesitation.
It may also effect Chart of accounts translations, and it may be required to enter translations for MainAccounts, as per new language.
you can decide which language to choose, by the maximum number of users, belonging to certain group of language or official language of country/company as per reporting needs
