Thi is actually something I like about ETW, regions are actually good in trades and it's usefull to just grab a region and sell it back for peace and some tech.I offer Gdansk back to the Prussians for peace, trade and an alliance, and they agree. It is an almost bloodless war for both of us.
This was an area that was sorely missing from Civ where the AI abolutely refused to trade or even accept cities unless they were gifts you gave them on their own while in previous TW games it was less trouble and more effective to just conquer and hold land and not give it back.