the problem is, the pahlavans are known for being good warriors and soldiers, not good governors.
As far as I know, the Arascid dynasty never actually did any important civil improvement. in fact, their few reforms were in the end detrimental to their dynasty, such as giving too much power to the satraps, which resulted in the rebellion of Ardeshir I and the destruction of their dynasty.
the current system makes expanding hard for a pahlavan player, due to lack of both good attacking units in the early-mid game and the sheer expense and difficulty of expansion.
I might be incorrect, because 30-40% of what I said above is my opinion.
however, making expansion for pahlava as easy as for Rome, will be overbalancing the game, and will reduce historical accuracy.
IMHO,pahlava had a sufficient Satrapy government, you shouldn't be able to recruit shivatir-e-Pahlavanig in egypt.
but this might just be what I think, and I am not implying your opinion is wrong in anyway.
this are matters of taste, not factual matters.
good day.
Tishtar