RTS-style building-unit requirements

[GriffonSpade]

An idea that has come to me is that buildings could be used to supplement technology as a requirement for buildings unit-types. This would also allow 'upgrades' to existing unit types when new technologies are unlocked, along with requiring logical technologies to build units, and allowing a reduction in unrealistic technology requirements for the sake of having troop techs making sense. At the same time it would remove a confusing web of technology upgrades for marginal unit improvements. My main problem with this is that there are no images for (most of) the buildings.

Example:

Archery technology unlocks Archery Range.
Horseback Riding technology unlocks Stables.
Bronze Working technology unlocks Bronze Smithy.
Iron Working technology unlocks Black Smithy.

Archery technology and Archery Range building unlocks Archers.
Bronze Working technology and Archery Range building unlocks Toxotai
Iron Working technology and Archery Range building unlocks Sagitarrii

This would allow Archers to first upgrade to the more expensive AND powerful Toxotai, but then the second upgrade would be more in the line of making them cheaper to build (Iron is notable for being /cheaper/, not stronger, than Bronze. It's Steel that's stronger than Bronze.):

Archers: 2A, 1D, 20 Cost
Toxotai: 3A, 2D, 40 Cost
Sagitarii: 3A, 2D, 20 Cost

Bronze Working technology and Bronze Smithy building unlocks Hoplites.
Iron Working technology and Black Smithy building unlocks Legion
(I've no idea why the vanilla Phalanx(Hoplites), has only a single point of attack. Hoplites were notable because they could destroy unformed armies.)

Hoplites: 2A, 2D, 20 Cost
Legion: 4A, 2D, 40 Cost

Warrior Code technology and Bronze Smithy building unlocks Phalanx.
Feudalism technology and Black Smithy building unlocks Pikemen.

Phalanx: 1A, 3D, 30 Cost; Pikemen
Pikemen: 1A, 3D, 20 Cost; Pikemen

List of buildings that would be useful:
Archery Range: Archers, Archer Cavalry?, Chariots?
Bronze Smithy: Bronze Heavy Infantry, Bronze Longspear
Black Smithy: Iron Heavy Infantry, Iron Longspear
Stables: Light Cavalry, Archer Cavalry?, Gun Cavalry?, Chariots?
???(Archery Track?): Archer Cavalry? Chariots?
War College: Heavy Cavalry, Gun Cavalry?
Siege College: Siege/Artillery

There are others for more modern units, but these come off the top of my head.

[cazfi]

Unit types have had impr_req field for a very long time so you can easily make ruleset like that.