So, is the thinking to simply blast south on autoroutes after Lux / Metz / wherever, right to Orange? 6-7 hrs.
I am making it my mission to take in at least part of the Route Napoleon on the trip somewhere. And Gorges du Verdon too, on Scotty's recommendation (would you believe Lisa and I were within just a few miles of there en route to meeting the original Stelvio 1999 crew at St Andre Les Alpes...if only we'd known...).
Probably makes sense to try this on the way out rather than way back, since the journey home requires the slog all the way back up through UK too.
The following would fit in Route Napoleon running south. Uses some of the Stelvio 1999 route from Besancon...
https://goo.gl/maps/lBHQ2
But to make this work, I think Saturday would have to be Lux / Metz to Geneva area - about 5-6 hrs driving. Hotel ibis Saint Genis Pouilly Genève would do the trick.
Then the rest to Orange on the Sunday. Again, 5 or 6 hrs - including some of Route Napoleon.
Gorges du Verdon is presumably a realistic "day out" from Orange, as some kind of loop. This, perhaps, which includes another wee slice of the RN...
https://goo.gl/maps/mmQsC
(albeit that's quite a day out for a rest day!!)
Slightly shorter version, with very little of the RN but still a grand day out...
https://goo.gl/maps/UzlEC
As for coming home.
8.5 hrs straight from Orange to Eurotunnel Calais on the Saturday. After Le Shuttle, pile round the M25 the same evening to enable Le Mans Style Start for home on Sunday. 6.5 hrs back to Central Scotland, all being well.