Questions to those who have mod experience:
How hard is to mode/add so that growth/food value change when:
a ) DoF signed?
b ) Has trade route?
I think its fairly possible... The first one would have to check each turn if it has a DoF and then add a dummy building for extra growth... I think its possible to make Trade Routes have an extra yield too...
Though, this would be my personal favorite:
UA: Manifest Destiny: +1 Sight for combat Units. +10% Tourism to civilizations you have a trade route with. Upon the discovery of Industrialization receive 3 Great Merchants.
UU: Minuteman: Stays as it is
UU: Pioneer: Replacement for Settler, ignores terrain cost. After founding a city, the Pioneer stays alive and may Culture Bomb (it may not found another city)