Should the Roman Empire accept all european cultures?
I have a converted CK2 save as the restored Roman Empire, controlling nearly of Europe (except Pomerania, who was my wife), and was expecting to absolutely dominate the world while learning the EUIV ropes. However, I found myself failing to colonize anywhere significantly except the edges of Brazil and Argentina, and I didn't get farther on the Eurasian front than Belo Ozero. After the Tengri reformation roflstomped everything east of Lithuania and Anatolia, as well as Egypt, the "story" of my CK2 playthrough was primarily the recolonization/reconquista of depopulated (Mongol culture) Russia by the disparate Catholic (yes, weird things happened) peoples of the Empire, but in EUIV my empire is constantly going bankrupt sustaining armies large enough to fight every stripe of rebel (except Protestant, oddly), and I fell miles behind both super-Abyssinia and MALI(!!!) spending my monarch points on culture converting the Baltic and suppressing rebels (yes, noobish mistakes):oo.
This may sound like the logical conclusion of such a flight of fancy as a "restored Roman empire", but the results of my EUIV game were at odds with the whole tone and the practice of the CK2 game, where branches of my dynasty (the Thormond Ua Brians!) controlled practically every kingdom title, and there hadn't been a revolt for 120 years before the end date.
Soooo, enough boasting about my super-awesome playthrough, I'm asking your opinions on whether the Roman Empire should get a bonus or have an idea (beyond "Pax Romana") that counts all "european" cultures as "accepted"? (Perhaps, given that crazy things can happen in CK2, it could be like every culture that doesn't have a non-Christian state or that has more Christian than non-Christian ones, rather than just along real-world cultural lines that hadn't formed in CK2?)
On a related note, what advice would you give me for getting a certain result from my second EUIV playthrough of this save, intending both to colonize Russia-Siberia all the way to the Pacific and at least the west coast of the Americas? (Africa is optional and Asia is ad-hoc)