What if the Empire Of Nicaea (the power that IOTL went on to reconquer Constantinople from the Latin Empire in the 13th century) was defeated by the Seljuks sometime before managing to reconquer Constantinople, such as during the Battle Of Antioch-On-Meander (1211)?
Who is more likely to conquer Constantinople afterwards? The Bulgarians, the Epirotes, or the Seljuks?
If the last option is the most probable one, then do we see an earlier turkish expansion into the balkans? Or do the Seljuks stagnate in Thrace?