Yes, Preston will send you to Tenpines for the First Step even if it's hostile!
So you have a fun idea, but there are a lot of gotchas to be aware of. Dodge them, and you'll have the immersive hostile Commonwealth in need of liberating that you envision.
The following is gleaned from 5 restarts in one week. Learn from my pain.
GAME START: follow KG's advice and start from the start, SimSet and Conq need the time in pre-war and the vault to Get Things Done. When the Conqueror pop-up appears, you need to make some changes to the default settings.
PRE-BUILT SETTLEMENTS vs. PRE-CONQUERED
Both lists have a default list on the left of "stuff will break if you change these." Don't change those. That includes Sanctuary - don't make it a pre-built, I know what you're going for but it'll make too many things too frustrating too soon.
Pre-Built just means it has a city plan already, and you want as many of these as possible, or you will have resource shortfalls and no one to liberate. Again, don't change the "leave alone" list on the left, but having all the rest selected as-is is fine.
GET SOME NEW CITY PLANS
The original, vanilla RotC city plans were not designed around Conqueror WRE play. They have resource shortfalls. They aren't supporting themselves at Level 1, let alone your soldiers. Vassalizing some of them will lead to a net LOSS of resources, as you gain more people than WRE value. Some of them will on day one be running at a deficit and need caps immediately. You'll need plans that have balanced resources, or, make sure plans with different resources are all in range of your first Outpost. You don't need all three W/R/E at one settlement, but you do need settlements with them all in range.
PRE-CONQUERED means a hostile force is occupying it. First you must choose which factions will randomly be occupying the world. You probably have a Minutemen faction pack? MAKE SURE TO MOVE IT TO THE LEFT! Otherwise they will be treated as pre-existing conquerors D:
For settlements, REMOVE TENPINES from Pre-Conquered,. or else The First Step will become A Much Later Step Oh God Run. My first attempt, i went over to talk to Tenpines, and got obliterated by a dozen gunners and 2 Mr. Gutsys. Oops. The vanilla Radiants and main questlines do NOT know what "conquered" means
. They WILL send you to hostile settlements for their quest.
If you really want to fine-tune this, choose two more settlements to NOT be pre-conquered. Abernathy is a good choice, Oberland another. One reason is to "get out of the way" of Preston's quests. Once Abernathy is a Vassal, for example, Blake tends to break and not react to the Returning the Favor quest, even if you go get the locket. The other reason is that the game needs to see three Vanilla Minutemen settlements minimum in order to have Preston offer Taking Independence. (You can get around this with a simple console command if you have to or you play for 20 hours and he never offers it, but one option is to simply start with 3 Vanilla MM towns.)
After you're offered the Castle quest, you can liberate those three settlements. Lore-wise, you aren't attacking the current owners! Rather, it's like a "settlement needs your help" radiant - when you arrive, it will be occupied by Raiders or Gunners or what have you. You need to do this becasue you'll need to create Vassals to supply your outpost, and the Vanilla settlements don't count. Even if you use a provisioner to satisfy the base Food/Water needs, that will NOT count towards faction pack soldier WRE needs.
If you're looking for a difficult, immersive "the whole world is hostile" experience, then you can leave every other location pre-conq. Note that this includes places like Bunker Hill, which means no access to that merchant right away; stuff like that.
CHANGE SOME VASSAL OPTIONS
By default, Vassals with city plans WILL NOT UPGRADE past level 1, and you cannot use the workshop at your Vassals. You need to change both of these. The former makes sense if you're a Raider gang squeezing the place dry, but less so if they're living towns you're protecting. Letting them upgrade is IMO more interesting and provides progression to the game. Also it may help with some of the resource shortfalls the plans have at Level 1.
You also want to turn on Vassal workshop access, because you WILL need to tweak things at them. If you leave this off, you can't for example add some farm plots at a Vassal when you're short of Rations. The Outposts only get HALF resource value from plots; so you need to focus production at your Vassals.
Preston and the Castle Radio WILL send you to hostile towns. There's no way around it. The vanilla system just doesn't know what's going on here. You can liberate the town and then speak to the questgiver; if it's a simple reward quest, like a kidnapping or whatnot, there usually won't be any issues even if the settlement has become a Vassal or Outpost.
Bottom line is: the vanilla system is blissfully ignorant of Conqueror and there's just no way to 100% preserve the vanilla MM quests' functionality, it's a trade-off for basically having a whole new game to play. You can still gain the Castle, make it your HQ, gain artillery, etc., and generally do the important stuff. Just be aware of how different the world's gonna be when everyone hates you :3
LASTLY,
For best results, build up Sanctuary as a normal settlement before you turn on Liberator. I know you want to jump in right away, but trust me, this will save you a LOT of pain.
Outposts get half plot value. You will struggle to build your first attack force if you take an empty Sanctuary and immediately make it an outpost. Rather, build a beacon, get a total of 8-10 normal settlers (the Concord 4 plus 4-6 more). Start by building 4 Agri plots and assigning all four Quincy refugees to them. Your goal is to have those plots at Level 2 before you convery to an Outpost; the newcomers should be put to work at a couple of Commercial plots, and one Industrial (i personally choose the Exvacation Pit so I can use the nifty foundations). I also tend to built an Armory and assign Preston to it. That will ensure you have the WRE to recruit Warriors when you declare war. Plots you already have functional when you become an Outpost are "grandfathered in" and will continue to produce their full value, and help equip your fledging Minutepeople.
