I suggest, like BP Jean, to avoid proximity of Paris: the circuit Calais > Arras > St-Quentin > Reims > Chalons/Champagne > Troyes (Your choice: Highways or National roads). Then, by N.77, join Auxerre. Here switch to N.6 towards Lyon. Cross over Lyon (easy by A6, free) and thread the Nationale 7 (sung by Charles Trenet) until the South...
Good voyage, from a very old motorbiker, till riding occasionally