The problem I have with the campaign is that it is still turn based. This system is so old that it should be abandoned.
What I propose is that there is a strategic planning phase where you plan on where the army would go to, what buildings you'd what to build, what units to recruit etc. Then after you click turn ends, the executing phase follows and your orders are carried out in real time. There should be enough turns in a year to allow you to reaccess your strategy and keep the balance of amount of battles happening.
What problems this solve? For starter, the unrealistic movement speed of army. Units no longer and teleport from one place to another to attack another army if given realistic movement for 1 year of time.
Then you could have generals with low courage or loyality refusing to carry out orders.
You no longer have to move and wait for a turn before you setup ambush and wait again to ambush another army.
There are just endless possibilities generated by making it half real time and half turn based.