Ah I see what you mean. Kind of like with your education modmod that certain buildings get certain benefits as you progress. I can work with that. If it isn't too much trouble to write out what you would do (because I have no idea how to properly balance out) and then I would go ahead and put it together
Here, let me make it plain:
Town Well
Cost: 50
Health: -1
Requires: Pottery, Masonry
Obsolete: Invention
Special Abilities:
* 5% Maintenance
* +1 Health with Public Works.
* +1 Health with Sanitation
* Upgraded by Artesian Well
* Provides Fresh Water
Water Pipes
Cost: -1
Health: +1
Requires: Canal System, Metal Casting
Obsolete: Never
Special Abilities
* 15% Maintenance
* +1 Health with Public Works.
* Provides Fresh Water
* Hamlet, Cottages, Villages, Towns +1 Gold
* Given for FREE by "Department of Water"
* +1 Production with Cement
------------------------------------------
Department of Water [National Project]
Cost: 600
Requires:
Canal Systems, Metal Casting,
Civil Service
Obsolete: -
Special Abilities
* 25% Maintenance
* Gives FREE "Water Pipes" to every city.
* +25% Production Speed with Public Works
------------------------------------------
Cistern
Cost: 105
Unhealthiness: +1
Requires: Sanitation
Obsolete: Steam Power
Special Abilities
* 5% Maintenance
* +1 Health with Public Works
* +1 Production with Weather Forecasting
* +1 Health with Chemistry
* Upgraded by Reservoir
* Provides Fresh Water
* Pastures give +1 gold
------------------------------------------
Water Tower
Cost: 150
Requires: Physics, Water Pipes
Obsolete: -
Special Abilities
* 10% Maintenance
* +1 Health with Public Works
* +1 gold from Farms
* +1 Happiness from Civil Engineering
------------------------------------------
[/QUOTE]
At this point, I just need to say, who on earth planned these buildings out? Their 100% wrong. Their so useless it should just be cut from the list.
Hand Water Pump
Cost: 250
Requires: Scientific Method, Water Tower
Obsolete: Replaceable Parts
Special Abilities
* +1 Health with Public Works
* Upgraded by Wind Water Pump
------------------------------------------
Wind Water Pump
Cost: 350
Requires: Replaceable Parts, Water Tower
Obsolete: Screw Propeller
Special Abilities
* 10% Maintenance
* +1 Health with Public Works
* Double production speed for Agricultural leaders.
* Upgraded by Water Pumping Station
Continuing on...
Reservoir
Cost: 450
Unhealthiness: +1
Requires: Steam Power
Obsolete: -
Special Abilities
* 10% Maintenance
* +1 Health with Public Works
* -15% City Defense
* +1 Food from Farms
* Requires a River
------------------------------------------
Desalination Plant
Cost: 600
Food +1
Required: Electronics, Coastal City, Water Pipes
Obsolete: -
Special Abilities
* +40% Maintenance
* Produces Salt Resource.
* +1 food from Farms
------------------------------------------
Fire Airport
Cost: 600
Health: +1
Happiness: +1
Req Techs: Fire Fighting, Flight
Req Buildings: Airport, Reservoir
Obsolete: -
Special Abilities
* 35% Maintenance
* +1 Health with Green Civic
Then, I think you should add some negative random events, to balance some of the positives these buildings give. Here's some rough ideas:
Event 1:
Poisoned Well
Requires Town Well in City
- Do Nothing
- Well is Destroyed, + 1

- Pay gold to dig a new well
- Lose between 75-275 gold.
- Frame a foreign traveler for the incident
- +1
in the city, -2 diplomacy with a random nation
Event 2:
Fluoridate The Water?
Requires Department of Water
- Fluoridate all City Water
- +1
in all cities, +2
in all cities, pay between 100-300 gold.
- Leave City Water Clean
- Temporarily gain +1
in all cities
- Fluoridate the water secretly
- +2
in all cities, pay 300 -600 gold
Event 3:
Poisoned Reservoir
Requires Reservoir in City
- Silence the Evidence, do nothing
- Clean the reservoir
- Lose between 150-400 gold.
- Investigate the incident
- +1
in the city, lose the Reservoir
- Blame Foreign Spies
- Declare War on Worst Enemy, gain 5 free Riflemen, +2
temporarily in all cities, lose the Reservoir
I'm sure there are a lot more ideas people can come up with, Events are easy to think up, but take forever to code in XML...