Ahriman
Tyrant
A few words about the unit maintenance costs:
I don't like the maintenance formula used in the vanilla game (cost depending on number of units and the current turn number using a complicated equation). Instead I made every unit have a gold maintenance cost, just like buildings. High level units have higher costs. Currently the cost of most units is 1, 1.5, 2 or 3 gold per turn, but it's subject to balancing. I even managed to make this cost displayed in tooltips and civilopedia
It seems the purpose of exponentially increasing maintenance costs was to punish the players who have too many units. But there is another mechanic that can do it: the unit supply limit. In the vanilla game it doesn't serve its purpose, because it's ridiculously high. I reduced it considerably, so you (or the AI) can no longer create "carpets of doom".
I think gold maintenance costs are enough even when they function linearly (like they do in Thal's VEM mod), I don't see the need for an extra separate mechanic that limits army size. The supply mechanic isn't needed.