If you play Sicily, Spain, and Portugal you will still have to deal with the pope and go on crusades etc. Making them very similar to the campaigns you have already done.

Hungary has a good unit variety and an interesting starting position, if you don’t mind leading a Barbie army.

My suggestion is for the Byzantines, because they don’t have the Crusade / Jihad option. Starting with Constantinople they are usually targeted by most of the other factions so you will see plenty of action and gain useful experience for your troops, ready to deal with the Mongul / Timurids.