I'd go Italy. The Roman empire, at its greatest extent, was still ruled from Rome I thought, and that it was only after it's peak that the capital was moved to Byz, though I may be wrong. The Germans are one of the significant reasons behind the collapse of the Roman empire, so that doesn't seem quite right.

Italy is like my 2nd favorite faction, England being the first. Italy has the gothic units, Italian Infantry, Genoesse Sailors, cheap ships, Hospitallers...I just like it.