I was thinking about mercenary camps to be in the game.
Just some tents with units in there, you can hire for money or goods.
They randomly appear close to your city and don't attack you.
This way the player could concentrate / focus more on economy (also with research). Although it isn't a waste of time to recruit some soldiers, this could be useful, also after loosing a battle with an enemy.
I thought mercenaries could be strong in figthing skills but have a lower morale, than self-recruited soldiers (if morale is implemented in the game, for this watch some Cossacks 2 videos on YouTube, to see how it could look like in a game, soldiers just run away if there are to heavy losses on their side).