I'd like to see a system that would help solve two problems:
1) A bunch of warriors and archers sitting around core cities in advanced ages.
2) A mass upgrade of units as soon as the enabling tech comes in.
My solution would be a to dramatically increase the base cost of upgrading a unit, but to slowly decrease that cost over time based on how long you have had the enabling tech. There would be a minimun % (say 10-20% of the base).
Example Upgade Discounts After Discovery of Enabling Tech:
Turns 1-10: No Discount
Turns 11-40: 3% discount per turn.
At the end of 40 turns the cost to upgrade the unit would be 10% of the base cost.
This would encourage players to upgrade their units before they discover techs that would make their cheaper upgrades obsolete. Of course the times, base upgrade costs, and minimun % would have to be balanced so that you couldn't just pump out a ton of Warriors and Archers, beeline to a millitary tech and then just sit back and wait till it was super cheap to upgrade them all.
1) A bunch of warriors and archers sitting around core cities in advanced ages.
2) A mass upgrade of units as soon as the enabling tech comes in.
My solution would be a to dramatically increase the base cost of upgrading a unit, but to slowly decrease that cost over time based on how long you have had the enabling tech. There would be a minimun % (say 10-20% of the base).
Example Upgade Discounts After Discovery of Enabling Tech:
Turns 1-10: No Discount
Turns 11-40: 3% discount per turn.
At the end of 40 turns the cost to upgrade the unit would be 10% of the base cost.
This would encourage players to upgrade their units before they discover techs that would make their cheaper upgrades obsolete. Of course the times, base upgrade costs, and minimun % would have to be balanced so that you couldn't just pump out a ton of Warriors and Archers, beeline to a millitary tech and then just sit back and wait till it was super cheap to upgrade them all.