Thanks for your help, your reputation precedes you.
Sixt is an awesome site with very user friendly pages. I looked but couldn't find any M3, at least at my locations. I guess a 1 series will do.
I also looked into the two locations that you mentioned. The South-Tyrol is interesting but pretty far away. Our trip will end in Milan so if I decide to take that route I will definitely rent the car from Lausanne, drive through South-Tyrol and return the car in Milan. The Black Forest is closer to Lausanne and if I take that route I will probably rent the car for a day and return it at Lausanne.
I am also in the market for a Panerai, especially a PAM088...but I will PM you with more details later.
I'm sure I will have more questions to ask the closer the trip gets.