The Regiment(or it's rough equal) is probably the smallest unit that a Fan Council should work with. That said Just so you don't get bogged down in details and since by the time you reach a Regiment you should have examples of every weight class anyway it really should be boiled down to as few things to track as possible.
I'm of a mind there there should only be two types of forces. Ground and Aerospace. It is possible to convince me to go to three: Conventional, Mech, and Aerospace. Warships would just be rolled into Aerospace "Regiments".
Each unit would have a three(technically four but the last is a bit redundant to track IMO) state damage progression(undamaged, light damage, heavy damage, and destroyed), a transport cost(I'm thinking a flat 1 for Aerospace per 30ly move, 2 for Ground per 30ly move), a support cost(2 aero, 1 ground), a loyalty rating(need something for civil wars and wars of independence), and two numbers derived from Green, Regular, Veteran, and Elite: A 2d6 modifier to progress the damage state of an enemy unit and a target number to meet or beat via aforementioned 2d6 check to progress damage state.
I still need to work out withdraw actions so that Regiments can be outnumbered but still have a chance to survive combat intact enough to either become a nuisance or get off planet.