This is just gameplay impressions, not stability or anything. Mostly pacing related.
a) I think food should play a role in maintenance costs for troops. You have more excess food, the cost of maintaining your army should go down (or lack of food should make it go up) I think mounted troops it should depend on the mount also.
With a lot of gold, and not a lot of food, I was able to maintain a large number of troops- it should require a balance of gold/metal/food
While I support the overall reesource/economy changes, I do think it needs some tweaking. Without certain resources, I can see civs falling behind fast.
c) Questing/exploring for goodie huts: The High-level goodie huts need to be more powerful to make it worth researching. It also seems back of spell knowledge isn't doing anything.