considering the scale of things having dedicated "units" would be rather odd, what'd make more sense would be control over doctrine, tactics and composition(which might be a bit like ship designing), it'd result in a much softer countering setup as units wont be super specialized like they're in most RTS games.
This would make army production into a 3 step process
1. Composition: Here you decided what makes up the army, stuff like mechanized-infantry, amphibian-Armour, fire-support (anti-tank/air if you'd like to split it), aviation and logistics(these guys would have a min value based on what is in your army, high maintenance=much logistics to be done).
2. Tactics: How'll the unit behave, it wont be autonomous but if you select a, say hit and run tactic the army will have an higher chances of retreating while still dealing more damage to the enemy then the enemy can do to them or you could have Charge/Blitz tactic which would make the enemy more likely to retreat or surrender. lets just say hit and run won't work all to well if the enemy is already going full speed at you.
3. Doctrine: not too dissimilar to tactics but way more specific, here's where you could make your army better at taking out enemy air or armor with fire support, for example. Anything that's related to or more branch types but not all types. More often than not making that one army better at using its own things against the enemy's things
This would make for something rather interesting planetary combat if it was refined a bit, just so that no opponent is alike.