"Remember, that the amount of the resource is given by the map, so the AI would in this case empty the mine spot faster than before. Aaand I dont think there are different config files for human player and AI, so a change affects you as well. Correct me if Im wrong."
Yes that´s right. I´m just changing i.e. the barbarians while i´m playing imperial-tribe. So i can fight against a stronger AI. But in this case i have to play against barbarians and can´t ever play against a strong imperial-tribe....
I also won´t change the output amount of the mines because of the problem you already said (although i could set the last of the three numbers to "100" so the mine will always find resources even if it is depleted ).
I´ll change i.e. the output amount of the axe-producer. For one coal and one iron they´re producing now 3 axes instead of one - ans so on. So they get a lot more and better soldiers.