TLDR: I made a mod to prove my ideas. Instead of being combatitive, please play a few games with a different flavor of balance, and then come back and critique the ideas 
The game in my opinion is a bit boring and bland. First, siege is too strong, leading to swift demises for castles, which in turn makes armies the deciding factor. As a result, a fight is quickly determined by a single battle, as well as harassment.
In terms of units, there is no tradeoffs. There is no reward for making a horseman over say a knight. As a result, archers, horsemen and spearmen are never seen after a certain point in the game. This results in armies of only knights charging around and clashing, because knights are the most pop efficient unit.
I made a mod to fix what I consider the most glaring issues, I called it the rebalanced siege pack. The result of the changes I made is a game mode that lasts much longer. Instead of being easily able to beat the AI in 20-30 minutes, I had a grueling match with several AIs on the hardest difficulty that lasted… 4 hours.
Before giving feedback on these ideas, please try them in game for yourself. The resulting game is a real challenge. What happens in this setup is that the forests are very quickly cleared, forcing people to send villagers out to get the last of the wood. Wood shortages naturally prevent abuse of siege engines, and since many trash units (archer, spearman, horseman) no longer have wood costs (but extra food costs) armies of low tier units naturally come to dominate the battlefield. Gold shortages also have a marjor effect, resulting in the deployment of extremely high tier units being drastically reduced. As a result, a company of knights is now an important and dangerous foe, instead of just another day.
In addition, lower tier units regen, while the higher tier units do not. This means that high tier units need clerics to support them, while low tier units can simply sit and regen. Low tier units are also not able to really do damage to castles, which forces people to either heavily invest in seige machines (which is actually very costly) or, they can go around the castles. The result with this is a battlefield that is much more static, (and fun) and there is an actual moment where opponents crack under the stress, instead of being just raided into oblivion.
The mod name is Rebalanced Siege Pack
Here’s my changelist:
- All civs have max pop increased to 400
- Castles and walls have regeneration. Walls 1 regen, castles 3 regen.
- Castles and walls have hp set to 35000
- All men at arms units get regeneration at .03 per second
- Mongol towers have regeneration set at 6.
- ottoman handcannoneers and mehters get .03 regen
- Mongol horse archers and horsemen get .03 regeneration
- Malian gbettos and handcannoneers get regeneration
- All trees now yield 60% less wood.
- All gold nodes give roughly 50% less gold.
- large stone nodes slightly increased to 5000 from 4000.
- landsknecht gets regeneration
- All horsemen have wood costs removed entirely.
- Rus horse archer costs from 80 food, 40 wood → 100 food, 30 gold
- Rus horse archers have regeneration.
- Horsemen have regeneration
- Mongol horsemen and horse archers have regeneration set at .05
- mongol horsemen hp buffed to match malian horsemen. Cost set to 150 food.
- Mongol horse archer HP buffed from 120-> 180
- Mongol horse archer damage buffed at level 3 from 10-> 12
- Khan regeneration, damage, and hitpoints scaled up.
- Rus and mongols can now get improved scouts in the dark age. Cost is buffed to 50 gold.
- Rus and mongol scouts foodcost 70-> 50
- All horsemen now cost 150 food.
- All traders cost an additional 5x gold to make.
- All traders walk 2x slower.
- villagers cost an additional 25 food, and have 35 hp (down from 50)
- farms have 200 hp (down from 300)
