I always routed via Troyes - Grenoble and through the mountains. I must have done that 6 or 7 times and never had any weather snags. Very attractive route and not many people you have to talk to.
Troyes is a total sleepy hollow but has Jet A1, the old town is lovely if you need to nightstop.
Grenoble (St George) has a slick little restaurant on site.
Try to find someone with the French section of Bottlang. Every airfield has its routes, especially for helis, and it has quite a good chart for the South Coast and its routes.