Simple; Add a disband button.
Outdated military equipment and excess personnel are regularly scrapped or brought back in to the civilian population after a war.
In-game this would be very useful, especially in larger maps if you have random units miles away from the front that are just draining cash. Implementation should be fairly straightforward, and maybe some refunds in both cash and reinforcements could be made if disbanding units in a town.
P.S. I'm sorry if this was posted before, it seems so simple that it should have been. I searched and only found a 2 year old topic that had no conclusion. I'm even more sorry if this is in the game somewhere but I'm just the idiot who hasn't seen it. I'm fairly sure it isn't though.
edit: so it's been posted many times before (I can't find it but ok), what's the conclusion on this?