Hm, nice itenerary, but did you consider taking a little detour after Genoa and visiting some of beautiful cities and countryside of Tuscany? OTOH, if you think you don't have enough time for town after picturesque town and prefer scenic routes instead, why don't you turn north after Marseille and do some driving through Switzerland? Then you can either get down to Italy via Como and Milan, or continue westward, skip Italy alltogether and enter Austria via Saltzburg. If you keep Italy, don't skip Venice, and perhaps round part of Alps from southern side, through Slovenia. (If you do that, a beer in Zagreb or thereabouts is not far away
).
BTW, touring the Europe in a Smart is a perfectly reasonable endeavor. I travelled (albeit somewhat shorter routes), besides my trusty Renault Twingo, in Citroën 2CV held together by wire, string, bubblegum and good will, in a Russian contraption called Moskwitch, and in an ancient Fiat van powered by 30hp 750ccm engine, among other things.
Ah, I am
green with envy!!!