AnnaLuisa, I remember that Silversea had this at one point, but not heard about it lately. You could choose ports and tailor your visit that may include one cruise, and a few days before or after the main one or your own itinerary that straddled both. As you can imagine, this is going to be a very expensive option!
I'm not encouraged by the report Karen posted. I never book "premium" cabins on Regent.
