Thanks for the answers Toady!
Right now you are moving to villain stuff, but I don't know if you are still going to look over the site interactions and since one thing relates to one another, well...
1. As your fort get more integrated in the world, how do hillocks interact with the surrounding biome right now (and in the future)? Will settling in an evil biome cause the hillocks that grow around your fort to have an undead/syndrome problem? Could they be overrun by the undead and end up with an invasion of your fort? Will you be able to send troops there to guard/fend off undead, beasts and such? Do sending troops there right now do anything?
Thanks Toady
Villians were discussed and necromancers fit the description of a villian but how that pans out with factors like re-animating biomes/necro towers conquering sites you'll have to pick toady's brains over because we have not a lot of clarity of a moment besides the shortlist on the monthly report without a devlog explaining. (See answer to question 3 for clarity about defenders in sites by transferring military dwarves)
Some of your questions, while it is important in principle to probe around the question for detail, wriggling in suggestions isn't recommended since we have a helpful subforum for proposed game additions. (anything that might be a percieved suggestions underlined, just for helpful reference)2. Tying to the previous question, will we be able to "refuse" hillocks settlements? And if that's the case, I imagine the system would work as charts, with migrants (or citizens of your fort) asking for a chart to settle a land nearby. ((You could deny them because it's too dangerous, for example)). How would the current count/barony system tie with the fact that hillock might not pop up because you denied them/place is too remote?
That's really a 2 and 2a) question but at the given moment with economic sites, dependency on you for safety from "villians" is quite likely so that you're not totally detached from the world, and just to, the current reasoning for infinite distance is that the offerings of wealth you give your caravan initially draws people from your civ to settle near you.
3. Conversely, how do/will hillocks interact with invaders? Could a necromancer rampage through the hillocks to try and raise a larger army to invade you? Would you be able to send patrols to try and intercept the necromancer before it snowballs in a huge army of the undead?
A lot of this pertains to a particular scenario rather than a question, though the scenario is a important one of whether enemies of your site will go attack your holdings first. In the current game its a case of if your holdings site is attacked, then the usual 'defenders' and attackers scenario, so you can already fend off attacks by transferring soldier dwarves (so i believe via conquerers occupying) but nothing professional at the given moment.
4. You are now moving to the "villain role", though I'm not sure this is "individual" (as in adventurer is a bad guy) or generic (goblins, "large scale bad guys"). Tied into that is slavery in the dev page, though only mentioned 3 times. Slaves right now are a rare occasion and only happen during site destruction in world gen. Since we have more assets now (hillocks) than just the fort itself, will that shift the paradigm of invaders to relate to all that? Let me give a few examples. Right now all invaders want your complete destruction, but it would make more sense for them to want your partial destruction just for their own gain.
Goblins already take slaves ingame, if you're connecting the link between expanded villiany options & roles from the devlopment plans, then a more fleshed out system may be possible, but im not saying anything imparticular because that's really for Toady to say and decide. Maybe it'll turn up as a viable development candidate, maybe it wont.
Questions 4.1 - 4.4 answered in enclosed spoiler.4.1 It's pretty easy to lock yourself right now and wait for a siege to pass (ignoring future tunneling units), but wouldn't the invading army raid/plunder the hillocks while you hide (which would also make the invasion last longer, since they have supplies)? Could a siege be done for specifically to gather slaves/undead without losing a lot of lives from the invading force while they force the army (you) to be shut in your fort or occasionally harass you if you try to stray too far away from the fort?
Enemy forces over time already do muster up forces, goblin particularly steal children for this purpose to keep population numbers high, as well as conquering any number of weak surrounding enemy sites. Inactivity
probably will be punished.
4.2 Tying to 4.1, what kind of problems would this cause for the player? Refugees you can't deny/or deny with consequences? The need to divert resources to reconstruct hillocks? Demotion from duke/barony status (can that even happen?)? Overall anger and sadness in your fort population by the destruction caused in their neighbors or isolation of being locked in the fort?
This is really a lot of questions but the overall theme is (if your holdings get trashed, how are you going to fix it?), Im sure Toady will have to, just wait and see for a response.
4.3 Will invaders ever attack you not only aiming for your total destruction? ((Could it be that they just want to carry off the riches they can and set out? Would some slavers drive by and just take your citizens then go off?))
You've already addressed this partially in question 4, and in the more recent releases, while your dwarves might be dead. A better rephrased question may be "Can invaders interact with your site in more than a political way" since the game conditions require all your citizens to be dead normally for you to relinquish your control of the fortress and 'lose the game'. Goblins & other civilizations can already demand artifacts from you.
4.4 With the upcoming villain stuff, will invaders use hillocks citizens to try and get to you? Could they occupy a site and hold it for ransom and convince a citizen to come to your fort to, let's say, pull the bridge lever when they come?
See my answer for 4.3 on more invader/villian interactions.
5. Will the role of "raider" get in this release? (In the sense of temporary forces, either outlaws or enemies, that come to take people or valuables, causing death and destruction but not enough to end the game)
One for Toady, though you could kind of either bend the question any number of ways. Repeating question 4.3 in the spoiler much.
6. Finally, are there respective plans for the stuff I asked in any arc, if it's not coming in the current cycle of hillock/villains?
Plans change, Toady might drop the first release of the villian arc and put it on hold if something better or complications come up in the way of something else (like a different direction for hill arc). Id recommend you re-read some of the FotF replies over the years as they had some pretty detailed explanations about the chronology of features for arcs.
Phew, i need a rest, i hope i could be of help.