There is a general consensus on this site that the Crusades are doomed, which I think puts a bit of a brake on TLs. Personally I'm not convinced and think that the transits of Anatolia of the Crusade of 1101, 2nd and 3rd Crusades could have changed the demographics of the Crusaders states and given them a shot at longevity, but I'm not much of a TL writer so haven't written a story.