Agree on all points, even if after reading diagonally the first time. And I would go one step further: instead of
create one product for each root directories..... For each one of the above, the root directory will be .../locales/en-US.
... I think it's the job of Mozilla to create it and it keep up-to-date. Note that /locales/en-US is ab_CD invariant, which means for time eternal (or at least as long I am involved) 80+ l10n white mice have been doing this labyrinth - under the expected noise conditions, again and again. And again.