Setting who you have to kill in ground combat

I'm pretty sure you can't do this, but I'm asking just in case...

Can you set which unit types need to be killed in order to capture a planet?

For example, say you invade an enemy world which has Troops, Fighters and Weapon Platforms in cargo. As it currently stands you have to destroy all these units in order to capture the planet. But can you change a setting somewhere so that you don't have to kill, say, the Weapon Platforms, but still have to kill the Troops and Fighters? But so that the WPs still take part in the combat.