Is it? A lot of what you're asking breaks the 20 Year rule especially in regards to the idea that Iran is trying to form a Shia Crescent, and I would question the idea that it was Post-Revolutionary Iran that had aggressive designs, considering the only conflicts it's been involved in are a vague and nebulously defined proxy war with SA and when it was invaded by Iraq in the months following the revolution.

That being said most of the literature I've read on Iran shows that the Shah and his father, whilst undoubtedly puppets (Although just how independent they were has become a point of contention) had an interest in Afghanistan and regional influence, what with the involvement in Oman's civil war.

If we go to the early part of the 20th Century then Iran's relationships with it's neighbours (and not so near neighbours) is more one of survival, with Iran's leaders "Trying to play Russian against English and English against Russian" and getting into scraps with the Ottomans and Afghanistan, and often losing.

Overall Iran's reputation as an never being colonised polity is partly true, partly misleading, it was undoubtedly subalterned to foreign states and made an active policy of compliance and collaboration with at least one of the regional powers. Even so, for a large part of history 'Iran' was often fractured, with local revolts and rebellions by governors or nobles being the rule rather than the exception, and the central state (such as it was) had to often be more focused on dealing with internal wars than going around the rest of the ME.

I'm mainly getting this from Abbas Amanat's Modern Iran, Michael Axworthy's Revolutionary Iran: A History of the Islamic Republic And Ervand Abrahamian's excellent works Iran Between Two Revolutions and A History of Modern Iran with a little stuff from Kurzman's The Unthinkable Revolution in Iran.