I can see the appeal of either style, maybe you can go with a bit of both. Some portions of the timeline could be a mock Skylitzes narrative of events with some chiming in from Psellos, and for other portions (particularly for those outside the scope of the Roman narrative such as events in Mesopotamia and Latin Europe) you can transition to a textbook narration, faux scholarly pieces, etc. It makes for a more diverse and compelling narrative in my opinion and gives the author broader range in developing the world.