It would have been great to see that. In Simcity 4, I remember we were able to build a customized Military base. I dreamed about it last night. You would have it as a specialty. You would start with an army base with different levels based on population When you reach the first one, you unlock the Military headquarters where you could plop an Air Force department (To unlock the airforce base), Navy department (to build a naval base), Intelligence (allowing you the possibility to launch satellites at the Space Center great works) and R&D which would function like the academy when you can research and unlock technologies or new vehicles. All of this available for the entire region like any other specialty.
In add of unlocking those buildings, you can mod your army base as well with hangars , ammo and oil depots, drill areas, barracks etc...
You would have also the possibility to add a recruitment center that would enhance the arrivals of new recruits and another specialty industry to build your weapons as well to export them for extra cash to your city.
Why not also adding the possibility of sending your troops overseas like we were able to do in Caesar IV?