Hello GrandViz (and Point Blank, since you are also in charge of the EDU):
The mongolian zero-upkeep units are unrealistic and unbalanced. I accept, that the Mongols should be able to support a large army even without having a settlement, since they have a lot of settlements off the map.
But I do not like the fact, that they can recruit zero-upkeep-armies.
I have two separate propositions to solve that:
a) Raise the Kings purse and let them pay upkeep accordingly. The Kings purse could be high enough to maintain their initial armies, thus simulating the unseen empire in central asia that finances them.
b) Another solution could be to make all newly recruitable units cost upkeep. You could introduce shadow units ('mongol foot archers' and 'mongol foot archers new') that cost upkeep and only these shadow units are recruitable.
Personally, I prefer option b) and I have modded every game like this. The result has always been satisfying. The Mongols still are a great threat but they do not acquire 30 stacks full of elite troops.
Regards
Notger.
BTW: I love your mod! I never allied-battles on the field, but now, the French have come to may aid, relieving a siege and even attacking an enemy stack neighbouring mine, thus creating an alliance battle. Great!