Here is another ten years of my test:

Parthia would be doing better if Saka and their super generals (100+ guys, 6-9 ceverons of experience) weren't beating them. Baktria is taking over some of Seleucids collapse. Good news is that this didn't completely cripple the big nations, it worked a lot like I wanted it to. Seleucia has dedicated itself to fighting Ptolemai, even retaking Antioch. They are also attacking asia minor. I think I'm done with this test, sitting around in Briton waiting for money is quite boring, plus there are better ideas than this here...

I like Eminos64's ideas, though. I have one thought on it though. Having the cut off point of 25 settlements is ok for the big guys and up and commers, but since there is a different script for each faction, maybe have each group have different range. Topping out the current and historically future big guys at 25, the rest of the civilized factions at 15/20, and the barbarians at 10/15. (All with the decreasing funds along the way.) That way groups that would have more difficulty administering large groups would have that difficulty represented by decreased funds sooner.