A fair perspective in a superficial sense but let us entertain the possibility of my being correct if only for a moment. In that scenario, could the Shahs or the Ayatollahs be better "entrusted" with being reliably and consistently hostile towards Arabs? As I recall, the elder Shah (let us disregard the big nosed idiot who claims the throne today) was a staunch friend of Pakistan, no less, and he was pragmatic towards both neighbouring Arabs and Israel alike. He suppressed Arab nationalist groups within Iran but was not directly at war with neighbouring Arab states (although he did provoke Kurdish separatism in Iraq on occasion I believe).
Meanwhile, the Ayatollahs had axes to grind, rightly or wrongly, with several neighbours. And eschatological religious perspectives are always easier to take advantage of by hostile 3rd parties than rationalised political narratives.
Anyway, I shall leave it at that for mere food for thought. Am no particular fan of anyone in the region frankly speaking. If it wasn't for India being a thorn in our side, I would favour a Pakistani imperial project to control all of the rest of them with an iron fist.