If you pan on visiting Bologna, you could also consider flying to Bologna, since it has a “real” airport with more flights than the airport in Florence, which by American standards would be considered just a step above a general aviation landing field.
Having said that, given your overall plan I would not bother to spend an overnight in Bologna. Thanks to the high speed train, nowadays you can reach Bologna in 36 minutes from Florence, less than many Americans’ daily one way commute to work. There is virtually a high speed train every 15-30 min connecting the two cities all day. Changing hotels takes more time than the round trip time between the two cities (pack, check out, carry luggage, travel, check in re-unpack, repack, re-check out….). You still get to enjoy the whole day in Bologna, without the hassle of changing accommodations.
For Umbria, since you’ve stayed in Orvieto already, I would consider staying either in Assisi or nearby Spello. Both are very quaint (Spello is smaller). From either you can easily drive also to Gubbio, Spoleto, etc. I’m not a big fan of Perugia. It reminds me too much of a big city (high rise apartment buildings, traffic, etc.). If you want to visit it, it has a beautiful and quaint historical center on top of the hill, but I don’t care to stay there overnight. Not even that easy to navigate with a car (if you visit, park on Piazza Partigiani and take the escalator to the top of the hill).
You are also planning to spend an overnight each in Radda and Siena. The two are very close to each other and I see no reason to change hotels in that case either. The Chianti Road (SR222) from Florence to Siena can be driven in 1h45min. Radda is about half way (a bit closer to Siena). Do you really need to bother with changing hotels 40 min apart? Choose one place and spend two nights.
And yes, I’m not fond of one nighters. I prefer to spend two nights in each hotel and day trip from there. Changing hotels, as I mentioned above, is time consuming.