Now that the food for walls feature has virtually but depleted available food reserves, I suggest having an option to train troops and tactics using gold. I always find myself with surplus gold. So, why not?
It's a good idea, as it'll help to balance overall resoruces
The devs would have to change one of the IG tips (one of the says: army marches on its own stomachs. So upgrade your mills to build a powerful army; or smth similar to what I've just written)
