suggestion: Dungeon Keeper 2 specialists, but Factorio engineers :)

[angrypidgeon123]

I mentioned "Also, Factorio is scifi, but subsurface could inspire from Dungeon Keeper :D though it's too much too ask since it's a game in itself, such as attracting (logistics) engineers and scientist by building certain buildings underground, such as a lab room, an assembler room making logistics, (war) engineers with an assembler room making turrets and ammo etc."

The way the feature would be simplest to make is exploiting this concept:

make any building that detects other buildings within its radius. This will be the underground "room" that unlocks a bonus by "attracting a specialist" as in Dungeon Keeper 2

How
I use https://mods.factorio.com/mod/Biter_Detector_Sentinel_Combinator
it finds incoming biters tick based, and I can set up its range via signal. Also AAI programable structures has a scanner for detecting buildings and zones but not very UPS friendly.
Point being there can be a building that can on demand or on tick detect buildings around it on a radius. Perhaps a modified beacon can do it as well, however the point is getting the number of buildings it reaches, maybe their content, and setting a radius for its search distance. Best to make the tick check every minute even (every 3600 ticks?)

1. "Scientist Level 1". Makes science 10% faster
   1.1. "Scientist Level 2". Makes science 20% faster etc. (cheaper also? dunno... maybe 5%, 10% etc. anyway...)
   How:
   1.2. "Scientist Level 1". Build (and have it at the moment of any research start), 5?10? labs in the detecting building radius.
   1.3. "Scientist Level 2". Build (and have it at the moment of any research start), 10?20? labs in the detecting building radius...

• Maybe an event "onResearch" exists, time at which subsurface can apply the bonus, or add it to the player bonuses somehow while the "room" exists
• perhaps the detecting building radius should inherit from turret so its radius appears on the map like for turrets
• the example is for simplicity, else it may confuse players as well adding more conditions than a number of labs, such as whether they are working too...

2. "Miner specialist Level 1". Makes mining get 5% more resources (I have a research that does it already, not sure which mod or whether it's a mod or vanilla. I think it's a vanilla feature)
   2.1. "Miner specialist Level 2". Makes mining get 10% more resources. Made the scale smaller because of existing technology
   How:
   2.2. "Miner specialist Level 1". Have 5 mining drills in the "room" detection building radius...
   etc.

• perhaps this progression should be limited at 30% for production type bonuses, and 50% for speed type bonuses

3. "Logistic specialist level 1 ". Makes inserters faster by 10% each level (never saw that before), or, increase their stack size +1 if all vanilla belts are produced (therefore researched already) in assemblers in "room" detection building radius...

• here could get more creative, just made it up from the top of my head
  3.1. "Inventory specialist level 1". Add +5 player inventory slots if a number of chests are in "room" detection building radius, and they contain perhaps 10K of 5 different items. Perhaps could be more granular like +1 inventory slot for each 10K different item kind

5. "Military specialist Level 1" Make turrets +5% damage +10% speed if having turret and ammo producing assemblers in "room" detection building radius...

• again, this need be limited perhaps to top 15% dmg and 30% speed perhaps, since they cummulate
  5.1. "Explosives specialist Level 1" Make grenades, rockets etc. do 10% more damage if building them in assemblers "room" detection building radius...

6. Production specialist level 1. Enable a special module type perhaps such as adding a technology researched in the tree. The researched technology adding seems a very simple way of adding bonuses using this idea

7. Alien specialist level 1. Copy some greenhouse buildings, give them a very high energy demand and make them produce "Lower enemy evolution" like Natural Evolution Buildings terraformer. Maybe 80 MW / minute second for lowering evolution -0.1 / minute, but unsure of the correct ratio to not make it overpowered. 80 MW is 2 fission reactors plus their neighbor bonus if I'm not mistaken. The specialist should either lower power consumption by 10% or speed up process by 10% to -0.11 evolution / minute. Actual numbers need work

EDIT: no, 80 MW is one fission reactor receiving 100% neighbor bonus, so 2 is 160 MW, therefore that should be the consumption per minute per second for one such "terraformer", at least. Lowering evolution is powerful so it should be costly. Also the neighbor bonus is cummulative so a fission reactor between 2 others will receive a 200% bonus. ENDEDIT

You get where I'm going with this. Basically for every bonus there is a "specialist" that can be enabled using this Dungeon Keeper 2 logic, and make the underground more interesting, plus creating incentives to build special sections like these underground

If achieving the underground "room" concept with labs and adding bonuses, expanding into a full blown array of features should be easy

EDIT2: well, maybe the room don't need to be also underground :D makes no sense. But the mod needs installed to get these features so that's something :D

EDIT3: about 7 and EDIT: 160MW per second to lower evolution -0.1 / minute (make a "produce" when that completed deducts 0.1 from evolution).