Some ideas for early middle ages Italia.
When playing 600 AD, Venice and Rome nearly always get sacked by Holy Rome. In history, Rome has been sacked post-600, notably by the Byzantines, but Venice was historically independent during the Middle Ages as a Byzantine vassal. I reckon they ought to receive far more initial defensive units, or Holy Rome AI ought to receive fewer offensive units, as Venice falling under Holy Rome so early on is not very historical.
Naturally, the logical fix would be to allow for vassalizing specific independent cities, similar to the Civ V city-state mechanic, but that would mean an independent "civ" for each independent city state, which...probably isn't good for performance. The other option is to make Italy an always-spawn to undo the damage.
Yet another idea is to have Italy spawn in 804 AD, with Venice as its capital, as the Republic of Venice, if Venice had not already been conquered by the Byzantines or the French. Then, if still Venice is still controlled by Italy, have Florence spawn and script-move the capital there.
Also, for history-sake and to fill a huge gaping hole in western Italia, if Italy doesn't spawn, perhaps Genoa should spawn as an independent city in place of Florence.
I also second the idea of Belgium. If there isn't enough room to put Brussels, the role of Belgium should pass to Netherlands. Upon finishing Trading Company, I also suggest that Leopoldstad should be auto-spawned in Congo under Dutch control. For being such a massive city in the modern era, it's weird to not see it represented.