I currently live in Imperia so I thought it may be best to head into France and then turn north, no?
I'm not sure about that. If you have the time, there's definitely an interesting route to be done through the Mercantour and Ecrins national parks, but it's pretty mountainous - and, my impression is that the mountain valleys form a sort of fan shape, so going north-south you are going to be going up and down a lot. If you were planning to hook round the Alps you have to go quite a long way west. Check the Google terrain view and you'll see what I mean.
You may have decided you want to spend more time in France rather than Italy, but if you haven't, then you might want to consider the
Bicitalia Svizzera-Mare route from Imperia and then either head for Cuneo, Pinerolo and then Rivoli, or going via Bra, or Alba, or Asti to Torino - and then take the Corona delle Delizie to Rivoli. From Rivoli you pick up the Ciclostrada Val di Susa which takes you to the pass at Moncenisio (or you could cross into France via Montgenèvre).
Alternatively you could go to say Nice and head north, crossing back into Italy. I think going via Isola 2000 and the Colle della Lombarda (col del la Lombarde) may be the most feasible option (the tunnel under the Col de Tende is closed to bikes and the alternative is a very scenic, but gravelly road).
I leave it to other people to comment on the route across France.
Do check out the link to Dave Davenport's article (last link in my previous post).