Capturable units

Certain units like Heavy Artillery and missiles should be capturable.

Say somebody is attacking somebody elses stack that contains missiles,those missiles would not be used in the battle, rather they would go to whoever won the battle. Missile-type capturable units can only be used when attacking.

Now lets pretend somebody is attacking a city that has artillery in it. Now, artillery should function like an entirely different unit class altogether, in that artillery cannot attack, and must be defended or they will be captured. When the artillery is attacked, it can defend, but it is up to the other units in the stack to ultimately win the battle, because if the other units in the stack die, the artillery is captured along with the city. Artillery-type units can only be used in defense.

I agree with the missile concept, but Artillery is useful for both attacking and defending in real life, so no support there.

Though I do like the idea that artillery can get overrun if there aren't units to hold people off of it