I would also like to recommend England, they are fairly enclosed, you can always just forge an alliance, using Caen as your way to getting close to the Pope, then just conquer england and focus on economy. Then later, send an army on a crusade or go and conquer any part you fancy, the AI doesnt seem to have the intelligence to use boats and attack england. The only AI i have ever seen use a ship is Portugal, and that was during a crusade.