The idea: A noble class assignment that allows the players to control/manipulate immigration.
The newer idea: Noble, legendary and commoner dwarf opinions about fortress immigration, and consequences for each.
Controlling immigration through a noble isn't a new idea, but immigration and what it entails could add yet another layer of depth to fortress society.
The conflict: Legendary dwarves versus less productive dwaves, and the nobility versus everyone.
TLDR Part:Legendary dwarves are a double edged sword. They built society, but they eventually don't need a society to back them up. In a mature fortress, it's nice that you almost never have to worry about legendary dwarves...but it causes you to worry more about the common dwarf.
Legendary dwarves essentially take food out of their mouths. A single legendary brewer/grower/planter/cook can do the work of 8 dwarves practically, and still have time to mingle.
So yes, let us limit immigration, for both game play and convenience reasons.
It could be handled essentially how Tropico 3 handled it. In that game, you build the immigration office. Working there requires a highschool diploma. You can set "Wide open immigration policy" "Only skilled workers" "Only specialists I hire personally to come to the island" and "Zero-immigration" Nationalist-faction citizens' satisfaction is in part tied to the immigration policy.
System:
Position: Dwarven Resources Clerk
Description: Needs an office and bed and dining room, 1 chest. While assigned, the Immigrants screen becomes active. You can then choose:
"Allow all immigrants"
"Allow no immigration"
"Allow only skilled immigrants."
and maybe "Allow only specialists"
The immigrants screen would also order all dwarves by their immigration wave. A DRC's work would consist of sending the required letters notifying the Mountainhome of a change in policy. (Their office would see about as much use as the Trader's office.)
You could further set filters for what KIND of skilled immigrants you want. You could set a threshold for skill level, saying they must be at least level 2 in some skill. Or you define only certain skills ex: only dwarves with Metalcrafting, a weapon skill or Brewing are allowed in.
Controls and balances:
The game, of course, isn't going to just keep generating immigrants within each wave until it creates the ones you want. You may almost never see immigrants because your restrictions are too broad. And the game will never start sending you competent+ skilled dwarves. So it wouldn't become a "farm for dwarves I don't have to skill up" mechanic.
Children and spouses of desired immigrants would be exempt from all the rules, so you'd still get a dwarf or two you didn't ask for. There's got to be some give and take when it comes to immigration, and allowing them to bring their families sounds like a good trade off.
Nobles, obviously, are exempt from immigration rules.
Opinions on immigration, and internal Fortress strife:
Everyone should have an opinion on immigration policy. The opinion should become active once a mayor is elected.
Nobles surely want all the cheap, rent-paying labor the fortress can handle (since those "overblown crafting peons think they shouldn't pay for anything"), and will prefer immigration remain wide open. That preference would hold true for all nobles (except perhaps the Philosopher, who can't be bothered with the mundane) because it's about ensuring there is always someone else to do the work. (Or perhaps not, if people think that makes for more dynamic and interesting nobles.)
When immigration is restricted or closed, the mayor and (duke, count, king) start getting unhappy thoughts of varying magnitude. One of them might mandate open immigration until they say stop. They are, after all, probably being pestered by the King to take some dwarves off his hands from the overcrowded Mountainhome, OR the King wants to prove how there's a place for every Dwarf at the new and improved Mountainhome.
The nobles would punish someone as normal for having a mandate ignored.
Legendary dwarves are an interesting category. They've got vested interests in a fortress they built with their own two calloused hands. They rightfully feel like they own the place. They get irritated when they go to create a masterwork and some sniveling peon from the Moutainhome is taking up the shop trying to learn how to make a bucket, or some witless idiot with no work ethic drops an armful of rock in the middle of the floor.
Legendary dwarves will prefer, in general, that immigration be set to skilled at least, happiest if it's closed altogether. Again, if people think it's more interesting that they can have all opinion types, that still works. But you want clear factions breaking down here so you get a sense of societal conflict...and I know if I could make 10 solid gold, gem-encrusted statues before lunch...I'd feel like I have a lot of political clout in a dwarf fort.
The Immigrants can have all opinion types, trending toward agreeing with the nobles (since they are/were immigrants.) Hilariously, they can oppose immigration too. Apparently the skill they first learned coming to the fort was self-entitlement. The immigrant population represents the x factor, the popular vote, and can add weight to either side of the controlled/uncontrolled immigration choice.
Either way, we would see a line like this in dwarves' thoughts.
"Urist McNewGuy doesn't like new immigrants."
"Urist McFriendly loves meeting new immigrants."
Perhaps when a dwarf becomes legendary, there's a chance their opinion on immigration will change.
Max pop cap considerations
Dwarves die. Maybe not if you're scumsaving, but in general you'll always be replacing dwarves, so the immigration policy stays relevant even at pop cap.
Pop cap control is less relevant, and useful, when you're maxed out period, but it wouldn't stop being a consideration. You're the new Mountainhome, after all, and EVERYONE wants to live there. Some people might want to leave open immigration at pop cap just for the fun of conflict, to appease dwarves as a tactical choice or because they expect (lulz) to lose a lot of dwarves at once.
Hi, I can already edit the .ini
And isn't technology wonderful. But that's technically cheating, and it would add to the game to make pop cap control part of playing it. And you can always just continue to cheat, and this mechanic largely means nothing to you.
This sounds like too much control
Not compared to controlling it through the .ini. I've recently noticed my fort stagnating and me running out of things to do....that's when I realized I hadn't changed the pop cap in two years. Immigration control filters and specifics can still be somewhat general. Think of it as:
Open Immigration - I want a large population that's constantly getting bigger
Skilled workers only - I want a medium population with steady growth
No Immigration - I want total control
So rather than letting players play with a hard number for immigration, like they do in the .ini, it gets abstracted.
And to be honest...I've never found the rush of a ton of immigrants interesting to deal with. Once in a while at the start of the game, they're a godsend. But for the most part they feel like an annoyance and something you'd rather deal with later as opposed to now. So losing some of what the immigrant rush brings to game would be replaced by what the immigration office would bring.
(PS-Immigrate, emigrate. Take your pick. Your fortress might as well be another country almost.)
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Using the immigration office to woo highly skilled dwarves to join your fortress
The Mountainhome (presumably) has all the awesome crafters you don't. Another job that could take up a lot of the DRC's time is trying to convince very skilled dwarves to come to your fortress.
System
On the immigration screen, press "s" for Hire Specialist. You indicate the craft, labor or military skill you want the specialist to be.
Whether or not this specialist is part of the next immigration wave, and how skilled they are, is a function of your DRC's skill level and the amount of time they spent working in the immigration office. You'd only ever get one specialist at a time, but it would be a good way to replace those highly skilled workers lost in freak accidents, misapplications of justice, sieges and the like.
When the specialist arrives, it would show up after "Some migrants have arrived" and say "Your Hired Specialist has arrived."
Enhancing your offer
Perhaps you're able to sweeten the deal too, by marking trade goods that become property of the specialist who chooses to come to your fortress. These goods would be stored in the Immigration Office and marked with [TSK]. The more and higher quality goods you offer, the higher the chance a specialist takes up your request. It makes sense too with the dwarven economy, when all dwarves are hard up for goods they don't have to pay for.
I don't see the use for that really. I have all the awesome people I need.
Again replacing dwarves. Consider also that military training and sieging are both about to become a lot more intricate. "I want to hire a crack Axedwarf who will lead training sessions to militarize half of my fortress." That sounds pretty kickass to me.
Other, even more optional insanity
What if craft guilds, as loosely defined as they are now, objected to specific job requests from immigration? Say the game averages how many dwarves have what craft skill, and compares that average to what requests are made on the immigration screen.
Jobs with a higher sum of dwarves x average skill level would send a representative to lodge a complaint with the mayor just like when umeployed dwarves do the same, notifying you that "The Mason's guild objects to your current immigration policy" and all dwarves with the Mason skill active get a small unhappy thought. "Urist VeteranMason felt like his job was threatened recently." You could choose to change your policy (which takes time and work from the DRC) to avoid further unhappiness, or you could just let the mason's guild bugger off.
That too would be a tactical decision, based on the skill of your DRC. How fast would you get masons immgrating? How many times would that make the Mason's Guild object? How badly do you need those new masons? Bad enough to skip general immigration altogether, and go straight to importing a specialist who you'll offer 3 *Masterwork Jade Bracelet* to?