Well if you going to take over the region anyways, I dont see a reason not to keep around the RCSs
They have a bigger army, consistently. You are unable to be able to start a takeover and get it finished as the other realm keeps coming and beating you in battle, so a possible solution would be to loot the RCs. That way you continuously get progress unless they go the spendy route of upgrading RCs to fix the damage, and when the RC is at max level they can't so it can at minimum cost them a lot of gold if they keep upgrading it, or eventually they start to lose the ability to wage war as effectively. Destroying a few RCs might not completely prevent them from waging wars, but if you take out enough, especially the higher quality RCs, they start to not have enough recruits to get a big enough army to keep beating and you can actually take over their regions.
There is more than one way to use the destruction of enemy RCs to your advantage/more than one reason. They keep putting decent militia down so when you go to fight, the other realm keeps winning, then rush there and work on destroying the RCs. While in my first example it was an underdog, trying to even the playing field, my second example was a more dominate force removing that advantage of the underdogs so the dominate force can no longer have issues. A weapon can often be used in many ways against an enemy. this is one that just happens to be underused, I believe because there is a lack of better generals.
A good general IMO isn't someone who is on every turn to give the marshals orders who then relay them, I consider that the opposite, because day-to-day operations of the army should be the marshals job in most cases. Maybe the general devised a special plan which works best with certain settings or something, but generally its should be the generals coming up with plans and strategies for the war while the marshals do the specifics of what needs to be done/responding to what happens.
