First up, 'christianic', 'crussaders', and 'furiosity' aren't words. I know this must seem a petty problem to you, but most of the other threads seem to avoid these mistakes. Second, go compare your scenarios to some of the better TLs on the board. Read 'Issac's Empire' and 'Raptor of Spain', especially the latter if you want to focus on Catholics. You know what they have in common? The ATL nations featured there had reverses at some point.
Same for Rome, the Mongols, and those other empires you keep talking about. Rome had Hanibbal, the Corruption of the Senate, various civil wars, and several bad emperors like Commodus or Caligula. The Mongols had the Japanese, the Mamluks, the Viatnemese and several family squabbles. Every major empire has civil wars, bad rulers, economic downturns and overextension as problems.
I've reread your posts (especially that large one with the map) and I've encountered none of these. Yes, you've establised that Kaloyan can turn eastern and southern Europe into his own personal polity, have a strong alliance with the Pope, exterminate the Greeks, turn the Knights Templar and Teutonic Knights and Cumans into an unstoppable military juggernaut that can do a 'Reverse-Genghis' and a 'Reverse-Black Plague' and turn China into a 'White setteler colony of the Kaloyanic Empire', but does it follow that it will happen?
Simple probability states that he or his sucessors will fail at one of those tasks, or even encounter accidents that cause a setback in their plans. Again, contrast this with 'Issac's Empire' or 'Raptor of Spain', or even actual history, in which reverses and crisises do happen to great empires. And no, don't reply to me saying that Kaloyan or his dynasty will always do the perfect thing to avert those problems, or that all the other nations will be idiots and sheep waiting to be swept up by the Bulgarian 'Manifest Destiny'.
Because that's not a proper TL. That is Draka.
PS: I'll probably get yelled at for this, and I'm sorry. It's just that I'm so fustrated that Mr. Rend violates everything I've observed from history and good ATLs, yet states that his vision is backed up by previous examples and historical forces.