Ive played a couple maps that were military bases, and I thought "Hey, why dont police or the army show up and do some damage?"
Depending on whether its military or just police can adjust what guns they have and what armor they are wearing, both being basic items, ballistic weapons, combat armor, etc.
And relations between PHALANX and the nation could determine whether the local forces attack you or support you, or "accedentaly" tossed a grenade at one of your men, killing him and the supposed alien target, heheh.
This could also tie in on the suggested idea of defending downed dropships