>>17799021 (OP)
>>17801363
The best chance for Iran to annex Azerbaijan would be the summer of 1993, when Elçibəy almost got couped by his own subordinate Surət Hüseynov and got replaced by Heydər Əliyev. Əliyev Sr. was open to the idea of turning RoA into an Iranian satellite state in exchange for Iran's help in retaking Karabakh. Iran was skeptical of the idea since it, like Russia wanted to leverage the conflict to control both RoA and Armenia. In this scenario however, if Iran agreed to this idea RoA would become an Islamic Republic, or Iran's Belarus.
Turkey would only give symbolic support to Turkists of PFA protesting against this move, since it was too busy with fighting the PKK on its own land. Russia would be slightly infuriated; Yeltsin could perhaps demand Iran to have a sphere of influence in Islamic RoA or fund the Russified underground opposition. The world at large would not care in the slightest, and the whole process would largely mirror the Iranian takeover of Iraq.
However in this case, RoA could be eventually sanctioned per Israel's request as an accomplice of Iran. The republic would be mired with political instability as popular support for integration with Iran, much less an Islamic republic was always abysmally low in Baku. Pragmatically speaking, Iran wouldn't want to actually annex Baku and therefore decrease the ratio of Persians in Iran's population; it always only aimed to subjugate the republic.