Cohen,
Site-specific units are hardcoded one to another : ie site X allow production of units Y and Z. You can recycle the Jotun sites if you use the units ID of the previously-Jotun capitol units.
Another good candidate is the Vale of Horses site : it's unique and normally produces the Horse Brothers units (relatively useless). Look at my Arco mod at IW to see how it's used for new capitol troops.
This good idea is from KO himself indeed
Only drawback is that if your capitol is conquered the conqueror WILL be able to produce the troops
, as the Vale site doesn't have the "capitol" flag
About the mod balance, I agree that most units are a little overpowered, with the leaders and Heroes totally off-balance. No human should have more than 15 hp or stats above 15 either.
But the idea is neat and I like it
