The First Order has an organization quite like what you've described. The Auxiliary.
Essentially it consists of former criminals, non-humans, and people who for one reason or another aren't good enough to serve in the First Order's Stormtrooper Corps. The lowest rank in the Auxiliary is a "Thrall", essentially fulfilling the role of a medieval squire. Ammo bearer, armor cleaner, weapons cleaner, the lowest tasks are often handed to the Thralls by both the Auxiliaries (The standard rank) and the Auxiliary Sergeants.
If you'd like to know more, feel free to ask!
I think I'm interested in this. Do you know if they do any sort of conscription?