Here are some that come to mind for me:
1. A Zanj success
The Zanj rebellion led by Ali ibn Muhammad al-Dibaj was a very powerful realm during the Anarchy of Samarra and had at its zenith in the 870s, control over all of southern Iraq, Ahwaz, the Nejd region of Arabia and control over the Hijaz region (loosely). Had this realm successfully managed to conquer Baghdad and or was lucky enough to have the Kharijite rebellion + maybe a Saffarid victory over the Abbasid, this domain could have become a very powerful entity over time. Ali ibn Muhammad Dibaj could in theory become a kind of messianic figure going forward uniting different heterodox sects of Islam under hos aegis and under the aegis of his immediate successors. In theory the 'Zanj' realm which would probably take the name of 'Imamate of Mukhtara' would become a kind of Arabo-Iraqi domain with a deep alliance with a class of freed slaves, Bedouin, Kharijite militants and Shi'a clergy. How long such a realm lasts is anyone's guess. The Abbasid would flee to Syria and probably submit as a vassal to the rising Tulunid state in Egypt. Meanwhile the Saffarid would resume conflict with the Imamate over Ahwaz and possibly over Mesopotamia itself.
2. Saffarid Neo-Persian Realm
Assuming the above scenario of Zanj victory and the establishment of an Imamate of Mukhtara, the Saffarid could be in position to create a long lasting Persian polity and possibly defeat the Imamate and conquer Mesopotamia, developing a sort of Neo-Sassanid border system. Saffarid position would be perfect for an alliance with the Tulunids against the Imamate in the center in fact and a victory by the Saffarid could see the rise of a Persianate Islamic ideal earlier than otl which truly began under the Great Seljuk.
3. Tulunid hegemony
The Tulunid ruling Egypt could quickly capture Syria and contest the Abbasid fleeing the Imamate and develop a powerful Egypto-Syrian domain, likely the new bastion of Sunni Islam in the region and the possibly the protector of the Abbasid Caliphate similar to the otl Mamluks, assuming they dominate the fleeing Abbasid in Syria. The Tulunid could then contest the Imamate of Mukhtara in northern Iraq and the Hijaz, leading to interesting wars between the two.
4. Qarmatian ascendancy
While the Imamate of Mukhtara, Tulunid and Saffarid battle, the Qarmatians could then likewise become a surging power northward or southward, creating a serious hegemony opposing all three and potentially becoming the ultimate victor in the entire conflict.
These above four present potential 4 potential realms that never situated themselves long from otl that could have quite easily become hegemons, even at the same time as the other three.
I saw a history documentary about the Hittites a couple of years ago that said that while their civilization collapsed around the same time as the Bronze Age Collapse, given their location it wasn't directly due to the BAC and everything that went with it but due to a civil war that kicked off around the same time due to backstabbing in the royal family. I can't help but wonder if, given the Hittites previous track record and how militaristic they were as a society, if they hadn't been busy with out of control infighting they'd have seized the opportunity to engage in a large scale land grab.
It depends. The Kingdom of Hatti was certainly destroyed by invading enemies to a degree, the Kaska and Muski and unknown assailants to its west were harming the kingdom and the Kaska-Muski captured Hattusa and forced the Hatti court to flee elsewhere, not to mention the Kaska and Muski destroyed the city of Ankuwa and in the past the Kaska had already conquered and destroyed the the sub-kingdom of Pala. If Hatti survived such strikes on it, it would have lost many of its allies to its south and would be decentralizing rapidly as loss of prestige would lead to princely autonomy south of Hattusa and Hatti. More importantly, the Kaska, Muski and peoples to the west will remain a threat, Hatti will need serious reforms to reascend in such a situation. Meanwhile, the Assyrians are still relatively strong and after the Assyrians-Karduniash defeat the Elamites, Tiglath-Pileser I will launch his campaigns into Syria and then into Anatolia and he may sack Hattusa and hence abolish that kingdom before it can reform. Maybe Hatti could ally with Assyria and or become its tributary and thus survive longer and become a rival of Assyria later.
Also and just finally, the post-Bronze Age Mid East was fragmented, but that does not mean it was easy to subdue. The Aramaen tribes and the many decentralized cities led by new Western Semitic tribal kings were perhaps more difficult to deal with than more sophisticated enemies who could be defeated and captured in battle and hence subdued in singular fell swoops like in the Bronze Age.