Jarlaxe Baenre
Emperor
One of the changes I would argue strongly for is that there should be a gradual return to neutral relations presuming no other actions.
It is rather silly that in 1950 you can have -x from "you traded with our worst enemy" when you traded said enemy corn in 2000 BC. And conversely if you and Alexander went to war together against the Persians in 300 BC how much should that effect diplomacy in the modern era?
Change each leader' memoryrand.