Hmm. These should be national wonders rather than world wonders.
Barracks: Military Tradition national wonder (Standing Army Headquarters) (costs Barracks *8, +1 XP to all units produced in city)
City Walls: Engineering national wonder (Scientific Fortification) (costs Wall *8, 2x speed with stone, +100% defense in this city)
Courthouse: Nationalism national wonder (Supreme Court) (costs Courthouse * 12, 2x speed with marble, produces 1 spy)
Forge: Replaceable Parts national wonder (Standard Weights and Measures) (costs Forge *8, produces 1 engineer)
Granary: Economics national wonder (Fractional Reserve Central Bank) (costs Granery *10, 2x speed with marble, produces 1 merchant)
Grocer: Refrigeration national wonder (Food Safety Agency) (costs Grocer *10, 2x speed with oil, +2 food in this city)
Library: Printing Press national wonder (National Library) (costs Library *10, 2x speed with stone, produces 1 scientist)
Lighthouse: Astronomy national wonder (Navigation Charts Project) (coastal only, costs Lighthouse *6, +1 trade route in this city)
Market: Assembly line national wonder (Consumer Culture Project) (costs Market *14, 2x speed with oil, produces 1 merchant)
Theatre: Mass media national wonder (Public Broadcaster) (costs Theatre *10, produces 1 artist)
Bank: Computers national wonder (Electronic Exchange) (Bank *15, produces 1 merchant)
Aqueduct: Medicine (Public Works Agency) (Aqueduct *10, +3 health in this city)
I think that places the "get one of X in every city" far enough away from getting the improvement that people won't just neglect building it when they get the technology.
On the other hand, it means that later cities start off with a raft of low-tech improvements right off the bat.
By making them national wonders, every empire on the planet can build them.
(Stone and Marble double production speed for various institutions. Oil helps build the physical networks.)