My thoughts:
Ravenna: Loved, loved, loved it. It was a combination of things: 5 or 6 churches with truly stunning mosaics. All but one easily walkable; the last is a short trip out of town on a public bus. I'm almost crying, thinking about the beauty of those mosaics, and I am not remotely religious. The core of the town itself is lovely and very nice to wander in. There were amazingly few tourists there in mid-July, given the attractiveness of the destination. And the Tourist Office was very helpful. Train time roughly 2 to 2-1/2 hours; it seems not to be on a major rail line--probably keeping the number of visitors down. This would be my first choice unless the idea of seeing the mosaics makes you roll your eyes.
Bologna: Large city with huge historic district. English-language walking tour available from the T.O.; don't remember how frequently. Many of the medieval streets are arcaded, so there's some weather protection. Museums if you need to escape the weather. Big foodie destination. Major university town; you may get lucky and run into graduation celebrations.
Lucca: Lovely, walled. As I recall, you can walk all the way around the town on top of the wall. There's something special about that, to me. I only had 2 or 3 hours there and want to go back.
Pisa: I've only made a quick stop to see the tower; my mother insisted. Last summer I met two residents of the city on the train. They sounded really frustrated that no one ever sees anything in Pisa other than that one area. They said Pisa has a pretty historic district. I haven't sought to verify that, but I will certainly do so before I next visit that part of Italy.
Arezzo: I visited for a day from Orvieto. Got lucky and hit a large outdoor antique market, which was fun. I don't know whether that market is weekly or monthly. I visited on a Saturday. There's a sizable historic area good for wandering but I'd say it's not as attractive as Ravenna's.
With just a bit of research you should be assured of good food in any of those cities. I suggest not eating near the tower in Pisa, though!
