How can you rescue peaches if you've sliced them before they are ripe?
I'm guessing you can't, but I'd sugar them and cook as pie or cobbler. I made a Cook's Illustrated Apple Crisp recently that had a neat trick. You sautee the sugared apples, then take apple cider and boil it until it is thickened and half volume and mix that into the apples before topping and baking for 15 minutes. I think you can try something like that using Kern's or other peach juice or puree. It would hopefully intensify the flavor.
You might try using them in something savory. Try throwing them into a veg curry, for example. Or perhaps marinate them in a bit of vinaigrette for a salad? How about pickling them, maybe using the Momofuku recipe for quick salt pickles? He says to toss with 1T sugar and 1t kosher salt and let sit for a while (he says 5-10 minutes, but I often do longer) rinse them, dry them and taste and serve or refrigerate, but I often find myself using more sugar and salt, leaving sit for more like 30 minutes, rinsing and then refrigerating for a bit, uncovered, to chill and dry.