Now my advice is, don't waste much time on this side show, cause the Alps are too easily defended.
Why go through the Alps when he can go around them?
If he cuts east he can pick up three more ports (Trieste is a size 6) and get due south of Vienna before heading north.
It's a little longer overland than the path from the Channel to Berlin, but what is there to stop him?
Considering how much of the German army in Italy is getting loaded up to pick potatoes in the States the opportunity seems pretty golden.
Open terrain for Patton to have a field day and where is Germany going to find any units to act as speed bumps?
Flying supplies is still pretty generous, and without much opposition those armored divisions will swallow up terrain fast (and defenders!).
The dam has broken. He grabbed 50 miles in the last week. If he follows that path Berlin is about 650 miles away, whereas your suggested Atlantic Wall invasion site is nearly 600 miles from Berlin, with lots of already built up fortifications in the way.
I wouldn't sit on my hands in Northern Italy in light of
capturing so many Germans. If they were still in some semblance of a line, maybe - but they're
gone.
"War is never a technical problem only, and if in pursuing technical solutions you neglect the psychological and the political, then the best technical solutions will be worthless." - Hermann Balck