I disagree… while I support some kind of auto-eco features, I think the same for military units would be counterproductive. Micro military units is one of the core and more fun mechanics of the game.
Maybe, a semi-automated feature comes to my mind while a writing this.
What if when you command a unit or group of units to attack an specific unit, when that unit is killed, then the next target should be the same kind of unit in LOS.
For example, I have a group of lancers. The enemy comes with a group of archers and scouts. I command my pikes to attack an scout. The scout dies, then pikes will target another scout as long as there were any in LOS if there is none then they target any archer.
This could be useful for the pikes owner but could be exploitable by the enemy too… So still there is micro and mind games involved.