The Padres aren't going to settle for Gonzalez. I don't think any deal happens without Casey Kelly (as Doubront projects to be a middle-of-the-rotation type at best), and I don't think Ellsbury gets the Sox as far as you think he does - after all, he's hitting his arbitration years, and the Padres are a cash strapped team, and Ellsbury's agent is Boras - so no long-term club-friendly deal. In fact, I think the Padres would prefer Kalish. Keep in mind that Jed Hoyer knows the Red Sox system inside and out, so we can't foist lesser prospects on him, and Lars Anderson's stock has not been really high as of late.
TL;DR version: I think it'll take at least Kelly, Kalish, Lars, and another top prospect to get the deal done. There is no way we leave the deal without losing just one of our high-ceiling prospects that have a decent shot at the majors (and Lars' ceiling is arguable given his performance this season).