The Garlean Empire is done, like Zodiark, Hydaelyn and the Ancients/Ascians. SE simply aren't interested in having anything really more to do with it, other than showing it's reconstruction. Also the majority of Imperial soldiers were draftees from conquered lands, usually stationed in the very countries that they were born in (such as Ala Mhigo having a lot of Ala Mhigan draftees stationed there) and most of the 'pureblood' Garleans went into elite positions, usually officers like centurions or legatee.