If the Giants rebuild, Brandon Belt might be one to consider. He's been mainly a first baseman, but has also played a passable left field over the years. His hitting stats have undoubtedly been depressed by the hitting environment he's played in. Peralta, who I also like as a trade possibility, has had his hitting stats inflated by his home field environment. Things to keep in mind.
Belt's contract calls for $16M for each of the next 3 years, his ages 31-33 season. It is the kind of contract that implies minimal expected surplus value. Which for me is an attractive thing because it implies we would not have to trade a premium prospect for him. He would be pretty much a salary dump for the Giants. If we can get Pollock (another one whose hitting stats are inflated by his home environment) for $16M/3 years, he would be preferable. But both the AAV and years might end up higher. In which case Belt would be a good alternative.
Belt and Pollock would both be 31 next season. Brantley would be 32. Peralta would be 31 for most of the season.