Troops should have the ability to be leveled as well. Not require as many materials as characters, but still have ability to ascend
When you get to Stronghold level 10, you gain the option to convert a level 5 building into a Barracks, which you can use to level up troops. Because it’s hard to keep up with raw materials, most people convert a forge. You can swap back and forth without any cost or losing levels on either building as long as you have a builder free.