I wouldn't think the deviation would be a problem for regent to florence, but will require a connection. We looked at transport for our upcoming trip from florence to room - might consider a driver to take you hotel to hotel and stop along the way at basically your choice like orvieto, sienna, Civita de bagnoreggio, winery or a combination called " From Rome to Florence and other Tuscan Towns"
runs about 900 bucks but save the hassle of luggage transfer on the train and provides a nice day of sight seeing.