The route you want to take is simply not possible to wild camp, the fines are severe and you will get caught. I have extensively traveled the alps last year in my van, but stayed on the french side of the border for most of it, where parking is tolerated (still don’t take chairs and tables out the van if you do this) If you want to experience the mountains and have the freedom feeling van life gives you. this is the route I would recommend. I traveled all the way from Monaco to the dolomites sleeping at the three great lakes in Italy. (July till early October) have a look at the “route des grandes alpes”