*koff koff*
A More Enduring Frankokratia *koff koff*
Point of divergence is that Henry of Flanders survives several more years and produces a son. I felt free to butterfly in some things which will prove very fortunate for the Latins, such as Ivan Asen II eliminating Theodoros of Epiros years before Klokotnitsa, etc.
The Fourth Crusade is my historical passion, but I think even in the best case scenario -- which is what I'm writing -- the Latins will assimilate. They were well on their way there OTL (as Blanche of Castile complained when she met Baldwin II, the last Latin emperor). The Latins simply lacked the manpower neccesary to hold onto their empire.