You could get the boring bit out of the way by heading for Caen, Argentan, Alencon, Le Mans and then Tours on the main roads/motorways.
then you could head for Loches, Chateauroux and the D990 to Gueret.
From Gueret take the D940A to Bourganeuf and the D940 through Eymoutiers and then the D979 to Meymac, then on the D922 to Aurillac, the D920 to Estaing, and then onto Millau to see the bridge.
Then head over towards Orange and Mont Ventoux. You then have a lot of options for the run East to Nice.