I've heard the quarries are interesting, not everyone is into mines but, I'd imagine the methods in cutting and how stones are graded have got to be fascinating. You'll need a driver/vehicle.
Pisa...lets face it, the VAST majority of people are there for one thing and it's pretty underwhelming. There's plenty of You Tube videos explaining the most overrated sights and I'm in complete agreement, Pisa usually ranks near the top. Pisa is a university town so, in general it's a younger population however the amount of tourists there to get a silly photo is pretty annoying and I couldn't wait to get out. If you absolutely must, get there in early before the mass of tourist show up.
Lucca on the other hand, was way more interesting and well worth the time spent there. The intact medieval walls, the narrow streets, the neighborhoods that evolved over time. I ended up staying nearly a week and very much enjoyed it. Lucca is also renown for having the best food in Tuscany, stick around for dinner and take an evening train back to Florence. If you get an opportunity, arrange a wine tasting session at Enoteca Vanni, their deep wine cellars in the middle of town have some fantastic history. If you're unable to get to a vineyard but, want to delve into some wine, Vanni and it's owner are top-notch.