Don't we already have the Inquisitor that does this?
Is he available at mysticism?
Edit: v1.5.3.
removes +1 unit cost, maintains +1 military unit cost (tribal warfare).
Keeping animals, captives, GP and workers will not cripple your economy the way it previously did.
Edit2: v1.5.4
Charity:
Banditry now have +10 crime in all cities and 20% in capital (was 15%).
Edit3: Something seems broken in my test game, all the AIs are going bankrupt and loose their units one by one in early ancient era. Maybe they don't build the buildings that give cash because of the large -% that affect them. I'm doing great economically (well I have to produce wealth in one of the smaller cities) with 4 cities that are further apart than the AI build them, most of the AI's have 4 cities as well.
So... perhaps I'll have to find a new balance with a lot less - percentage but higher maintenance costs.
What do you experience in this area?