I would ferment 5gal of store bought juice dry, then backsweeten with a couple quarts of blueberry juice (Wymans or knudsen "Just Blueberry" will do from your local natural food store) and with either blueberry-pom or apple frozen concentrate from old orchard(I usually use 1-3 and 1 extra after sweetening to taste for carbonation). This is a pretty solid way to make any flavor you want. If you bottle, you will have to pasteurize though. It's not complicated, or that dangerous, if you do it correctly.