Yay, someone else interested in the Assyrians!

I have actually considered doing a TL on this very topic (one of the three major TLs I want to do, the others being a Roman one I'm currently writing and an Indian one which is still in the planning stage), so I've given this some thought.
Well, if we're talking about the Neo-Assyrian Empire, the latest possible POD would probably be some time during the reign of Ashurbanipal. We either need a competent successor (as opposed to Ashur-etel-ilani and Sin-sharra-ishkun) or some way to get rid of the Pyrrhic struggle against Ashurbanipal's older brother, Shamash-shuma-ukin.
Another way, if we want to get creative, is to make Esarhaddon's original crown prince, Sin-iddina-apla, not die before his father. We know basically nothing about his character, but with some artistic license we can make him a brilliant administrator who manages to reform Assyria's bureaucracy, giving his successors the stability necessary to go a-wanking.
Edit: Now that I think of it, Sin-iddina-apla and Ashurbanipal could actually make a pretty decent team. Ashurbanipal was, by Assyrian standards, kind of a nerd (it's believed that he was the first literate Assyrian king). If Sin-iddina-apla focused on being the overly macho, overly brutal badass warrior king every Assyrian prince aspired to be, Ashurbanipal could stay at home and improve the efficiency of the state.