I've never actually played a Galactic Civ game, so I'm basing this post purely on research off the GalCiv wiki.
So from what I learned from GalCiv2, planetary invasions are done first by eliminating any enemy ship in orbit (a ship occupying the planet's tile) and the moving a troop transport onto the planet. Depending on your soldiers (morale, tech, mini-soldiers) and a chosen tactic, the game rolls your odds against an enemy planet's soldiers (morale, tech) and planetary defenses. The victor of these rolls captures the planet.
I was wondering how planetary invasions would be portrayed/handled in GalCiv3.
Personally, I would appreciate diversity in ground forces, maybe 3 classes of ground units - infantry/armor/support (or artillery). Depending on how they're used in an invasion your odds go up? Perhaps even a little more depth to planetary invasions?