regarding previous comment maybe as a penalty you can do something like "every time you make an alliance another army makes an alliance with an opponent" but they have to be alliances that makes sense (aka both kinds of elves instead of men of the west and demons)
nobody will see this damm comment but its worth a shot and i might get a reply in like a year... HOW TO BEAT THE FREAKING THIEVES? they are so damm op! my character is just stuck sitting in windy village now...