How do I make facilities that allow certain facilities to be placed atop them?
I would think you could just create new facilities that did a combination of different things. Like it was a 4 story height map section facilities on the bottom two floors, and additional facilities on the top two floors (thinking TFTD 4 story facilities here).
I dont think that the initial base should necessarily start with these, but since you pretty much only get 1 of each thing at the beginning it would be an excellent way to expand, and a boon for new bases.
New Facility Suggestions
R&D Labs (2x2 Facility)
Provides: 100 lab space, 100 workshop space, 200 living space.
Construction Time: 34 Days
Cost: $2,350,000
Maintenance: (just add up the maintenance for 4 living quarters, 2 workshops and 2 labs)
So you build just 1 of those and you're pretty much set on R&D for that base. Makes sense just to have all those guys cloistered together.
Armoury (2x2 Facility)
Provides: 250 Storage, 100 living space.
Construction Time: 25 Days
Cost: $750,000
Maintenance: (same as 5 General Stores and 2 Living Quarters)
Here you have the bottom two floors being one giant General Stores area with soldier spawn points. The top two floors have one normal size General Stores in the center, with the periphery area around the center part containing living quarters. There should be no HWP spawn points on any floors except the bottom.
Ultimate Defense (2x2 Facility)
Provides: 5000 Defense power, Grav Shield Effect, 100% chance of hitting
Construction Time: 48 days.
Cost: $6,500,000.
Maintenance: (4 Fusion Defenses + Grav Shield, all multiplied by 1.25)
Combination of Fusion Ball Defenses and Grav Shield, pretty much protects that base from ever being invaded. But at a heavy cost. Still possibly more economical on space and initial price.
(this is one of those things you could build later in the game when you have tens of millions, and you just dont want to be bothered with base defense anymore. Still, balancing this is its extensive construction time, so its not like you can just plop one of these down and have it ready if your bases are getting attacked)
Additionally you can provide passageways on the 3rd floor between each of the facility sections, similar to how in TFTD the multi-level alien bases had connections on other floors. That way you could technically have aliens on other floors, but the idea is having the equivalent of maintenance halls to get around places that might be heavily defended.
I mean on the map sections you can put anything you want in it, but this even keeps it believeable. And as for packing everyone together like sardines, thats life in a nuclear missile silo or submarine too.