I thinking about my own "scenario" (not historically accurate, rather ASBish... there would be some combination with fantasy and/or horror...) based on high medieval ages, where everything is bigger and cooler. Emperor is more powerful, various merchant guilds are more richer, crusades met with more success, chivalric orders play bigger role in... almost everything (maybe templars weren´t dissolved?) and mongolian invasion done even more mess... Um, and "age of discovery" start a little sooner, and sailors from Italian, Flanders or German cities conquer western "paradise"...
And that fantasy side of thinks... There should be definitely fantasy elements, but mostly based on real history myths and beliefs (werewolfs, sorcery, alchemy or strange inventions of philosophers like Roger Bacon), chivalric romances and epics (like arthurian cycle, Orlando furioso or Nibelungenlied)...
Hohenstaufen were more successful in founding long lasting dynasty, find some consensus with church and even were able to unite western and eastern empire! Well, at least theoretically, because power of emperor still remain limited, except Kingdom of Sicily and Constantinople with few adjoining provinces, administrated by (usually) loyal italo-greco-arabian bureaucracy. However, Hohenstaufen ruler is not only emperor of east and west, but even king of Jerusalem and protector of god´s grave, what make him head of christianity (or co-head, with pope)!
In Italy, which is theoretically center of power of western empire, they are strong city-states, TTL naval superpowers, stuck in complicated love/hate relationship with emperors...
North is too far from residences in Constantinople or Palermo, so is even more freely subject to Staufen. North of Alpes, there are some duchies ruled by Hohenstaufen cadet branches, like their old home, Swabia, but north Germany is dominated by powerful guild of traders and craftsmen, the Hansa. Single north city cannot compete in wealth with Venice or Pisa, but together, they re one of strongest forces of this world.