Semi-fancy tactics in Strategic Combat?

[Blueentity]

I have not found away to knock down a plant to a certain percentage and then leave it alone in strategic combat. Unless I have a ship with troops, the ships happily glass the planet if they can. I have tried this with:

Various weapons (direct fire and missile)
Various combat strategies (Optimal Firing, Capture Planet)
Various % on “Damage Percent Per Planet” (10% to 100%)
Toggling “Damage targets till all weapons gone” (on and off)

Of course I could chose “Don’t Fire On Types”, but there are times, especially in the early game where you are short on troops or trying to inflict some unhappiness, where you want to soften up a planet without destroying it.

Also, is there anyway to have the troops land on the “Biggest” planet instead of a moon? Choosing “Largest” or “Strongest” doesn’t seem to make a difference.