For those who haven't read it, in The Shiva Option there's a planet so massively fortified by genocidal aliens that the protagonist side ends up diverting an asteroid on a collision course, because any frontal assault would be suicide. Diverting the asteroid takes months, and could be stopped by the enemy warships, but the friendly fleet escorts it in - it basically forces a naval engagement instead of just defending the planet since the hostile ships have to come out and try to divert it.
I don't think an option like that is really possible or necessary in Aurora. You can always, as you note, bombard a planet with missiles from outside STO range, since there isn't an option for ground units that launch anti-ship missiles.
As I understand the system, if you're faced with an ungarrisoned enemy colony, you can just vaporize it with beam weapons at essentially no cost (maybe a few MSP due to the new weapon failures), or you can bring in enough troops to garrison it and gain a functioning colony. If the colony is defended by ground forces, you have various options:
1a) Destroy it with missiles from out of STO weapon range. No danger to your ships, but costs missiles (potentially a LOT of missiles if the planet has large numbers of CIWS ground units). Enough CIWS relative to your fleet might eliminate this option, though I imagine it would be cost prohibitive.
1b) Destroy it with beam weapons. Means you'll probably take some hits from their STO weapons, but it would be in many ways similar to a fight between warships.
2a) Bombard the ground units with missiles, then invade. This will destroy a lot of the stuff you're trying to capture since missiles inflict more collateral damage than beams and (I think) the STO weapons don't reveal themselves until they fire, so you'll have to bombard all the ground forces.
2b) Engage the STO weapons with your warships, then conquer the planet with orbital fire supporting your ground forces. Like 1b, involves a fight in which some of your warships will probably be damaged if not destroyed. Inflicts less collateral damage and wont use up your missiles.
2c) Launch an invasion unsupported by orbital ships; you might lose some troop transports to STO fire but hopefully most will get through, drop their troops, and retreat. Will likely inflict the least collateral damage and give you the most loot captured buildings.