What if Iran, in its exact current geopolitical position, was a fully industrialised country, capable of producing its own technology, agriculture, weapons, and material goods, and didn’t have to rely on outdated technology and importing goods from other countries? And its economy wasn’t resource based. What would it’s economic and political impact on the Middle East, and ultimately the rest of the world be?
With a strategic point on the Indian Ocean and especially the Persian Gulf (control of much of the world's oil), Iran is already very strategically important. If we assume some Iran-wank, where the Qajars are reformed with few problems (Constitutional Revolution of 1907 goes insanely well or something, and isn't reverted by external influence), and a worse Great War and Russian Civil War causes both Britain and Russia to have even worse fates than OTL, and Iran can somehow capitalise on everything based on these facts, then Iran is powerful indeed. Bahrain, which was once ruled by Iran, should stay under their rule as an autonomous region (but their economy controlled by Iran).
As historically, Iran is easily the hegemon of the Middle East in this situation, as they're striving to be OTL (opposed mainly by Saudi Arabia). With the population, economy, and resources, no Arab state can match Iran, except maybe Egypt. For Muslim states, only Turkey (if it isn't Ataturk-style secularist) and Pakistan (if it even exists) could challenge Iran. Iran also has the incentive to minimise religion (to prevent Sunni-Shia conflict, as a Sunni minority exists in Iran) and maybe go for a Russian alliance in the mid-20th century, opposing the British (the 19th century defeats of the Qajars, which lost the Caucasus and bits of Afghanistan, probably won't be reversed no matter what Iran does) and other Western powers. A stronger Iran and a suitable ruler--Republican, Qajar, or even Pahlavi--could potentially stand up to any US coup pressure and if the US still tries for a coup, could cause major embarassment for the US.
But a non-resource based Iran is hard. Oil and natural gas will always remain big in any Iran. There's also other mineral resources which Iran can (and does) exploit which renders such an Iran challenging. The most realistic Iran would probably look most like modern Russia in terms of economy. I'd replace the various "religious"-based "charities" in Iran with other groups, preferably nationally-owned groups which actually provide welfare and charity (or just good jobs with good wages which benefit Iran) instead of helping facilitate government corruption in among the worst possible manners. If they must be corrupt, then just have the equivalent be "Iranian oligarchs", created after some ill-advised privatisation. Oil wealth in good times should be used to build the base of other potential economic sectors.
The overall (and best) result could be about 82 million Iranians (but with the demographic transition having been much earlier, and the population growth almost static) and a GDP per capita over twice OTL Iran, thanks to this alternate Iranian history, no revolution, etc. That means a GDP per capita of perhaps 11-13K, and a total economy of over a trillion dollars, about that of Mexico and Indonesia. A moderate Iran (if they're officially religious, they aren't overtly so) could promote themselves as a stable anchor in the Middle East, and with their energy sector (fossil fuels and later solar energy) be a great ally for either the USSR or the US. Iran would perhaps be best in charting a non-aligned policy (historically Iran suffered greatly thanks to being divided between British and Russian influences), but a lot depends on what the US and USSR/Russia do in the region, and potential rivals like Iraq (who would never dare attack an industrialised Iran) and Saudi Arabia do. If Israel exists, then they should be of no concern to Iran, as Iran should maintain it's Jewish community and what they have to offer for the country.
This Iran would have some indigenous defense industries (which could see exports in the Arab World and Africa), but would also in parts be relying on the US, USSR/Russia, and China.