Some ideas for the "One big expansion pack"

[NotRexButCaesar]

there would be a “1 best solution”, which does not currently exist.

robots.

they are unconstrained on throughput potential- unlike belts or trains, which top out at a fixed speed, bots will go faster and faster until they are instant.

I do mostly play with belts, but there can be challenge in bot builds too.

[Redpossum]

Missile Turrets?
Gun Turret wagons?
Missile Turret wagons!

[eradicator]

Missile Turrets?
Gun Turret wagons?
Missile Turret wagons!

Wagon-missile turrets?

[Mskvaer]

Just a quick and small thought: Walls made from Concrete, not Stone, are much harder, and more with refined concrete.

[NotRexButCaesar]

Just a quick and small thought: Walls made from Concrete, not Stone, are much harder, and more with refined concrete.

+1. A wall with more health would actually be very useful: not because it can more damage, but because it has a higher path cost for biters. Dragons teeth and other funnel like structures would benefit immensely.