Mercenary Barracks (For those who lived through battle)
The Mercenary Barracks would provide an avenue for troops that lived through battle to re-enter the players game. As all mercenaries do, they would cost gold. We currently have troop-cost across all resources with exception to gold.
Ideas for how the Mercenary Barracks would function:
1) Only your troops that live through battle would be available
2) The cost could be a flat fee to buy all troops available or buy a group/ type of unit
3) The troops could have no build time just buy and use (after all you did train them already)
Implementing the Mercenaries
They could be added to current troop camps or maybe as Mercenaries they have their own troop camp... The band of renegades live separate from the new troops thus allowing the game to regulate how many you can use at a given time.