Let's talk a little more about the implications of Outposts and Colonies and 4X play here, in terms of new play opportunities.
Raiding Players, pirates and privateers might all want to engage in raids of planets, to gain resources and to do some minor damage to enemy economies. Gameplay, ideally, would have players picking a location on the planet to raid, with some information about population density and risk; depending on whether they're raiding a well-defended location like a city or a military base or somewhere sparsely-inhabited, their risks, treasure-haul and defenses met might vary considerably. For example, it's probably very safe to raid the middle of nowhere, but you'll be lucky to pick up a few Supplies for your trouble; raiding a small community might gain you a lot more treasure, but you'll probably get ID'd and you'll have to fight, etc., etc.
The whole point of Raids is to gain treasure; they should do a little damage to Stability (if that remains a thing) and minor resource damage, but that's probably all.
There should be a Skill for Raiding, generally covering:
A. How stealthy you are, i.e., how likely you are to get ID'd and intercepted.
B. How much loot you get.
C. How much Stability loss you inflict... if you choose. I think that should be a choice; a good, clean Raid to gain resources is probably not very damaging; a deliberate effort to do some collateral damage on the way out is more important. Raiding a location repeatedly ought to create serious Stability problems, but it should take a lot longer than Attacking (see next).
AttackingAn Attack is very different from a Raid. Raids are primarily about gathering resources; Attacks are about destroying enemy assets and seriously disrupting Stability. Attacks have a specific objective; perhaps it's to destroy a facility, kill population, engage the local defences, etc., etc. If the Attack is successful, the direct damage is done and Stability is impacted pretty sharply.
However, given that Attacks are almost always going to be directed at major locations, they're very dangerous and risky, and they won't give the player much loot, if any, because they're trying to get in, do damage and leave. So Pirates generally don't bother and the player probably won't until they're in an interstellar war... either because they have founded a Faction or because they've taken a Mission (these should pay well, since they should be very dangerous indeed).
Invading Invading a location ought to be very difficult. Essentially, your chances of pulling it off with anything less than overwhelming force and a lot of time should be nil unless you've degraded the location's Stability quite a bit. It shouldn't be easy or fast, especially with Markets over size 4 or so.
Invasions, if successful, give the player captured equipment, goods, tech and a population that, while initially hostile, might become accepting of the player's government over time.
Generally speaking players should not get to participate in Invasions until they have founded a Faction; this is strategic-level warfare. Invasions should start with the "space phase", where the location's existing defenses attempt to defeat the player's fleet; if that doesn't work out, then the player can then begin the "ground phase", where they're going to have to engage the ground defenses at the key sites. Once those are defeated, the invasion begins, and then it's mainly a matter of time, resources, etc... while not letting the enemy break the siege. Invasions should be pretty rare, take a long time to pull off, and take even longer to convert the population to friendly (i.e., get Stability under control).
Destruction This needs to be talked about, I think, since the lore's got Planet Killers in it.
1. Destruction should involve a MacGuffin that is pretty fragile, can't be deployed quickly, etc., etc., so that it's not completely preferable to Invasion, even for blood-thirsty players. It really can't just be, "you walked in with nukes, everybody died, great, this planet's yours" or it'll be a little too tempting to just glass everything, especially once you have all the Tech you wanted (see:
Stellar Converter).
2. Destruction should be, to put it mildly, "frowned upon" by all Factions (heck, even the Pirates). I don't think that using one should be without pretty important diplomatic consequences; even the staunchest allies should be effected; you've just killed thousands to billions of people and have perhaps wiped out precious archeotech that cannot be replaced; it really shouldn't be a commonly-used option, more of an act of desperation.
