Who know's how it will turn out. It won't taste like mango juice with a kick though... it'll ferment dry. I would ferment a base apple cider, stabilize (ie kill of the yeast using k-meta and sorbate) and then experiment with a small portion of cider to see how backsweetening with mango juice works.
I was wondering about this same issue when I saw mango juice in costco. I decided to make a traditional mead, stabilize and then try to backsweeten with mango juice and honey.
Relax, don't worry etc. and so on.
Primaries: Old Ale, Barleywine, ESB, Scottish 80/.
Secondaries: Lime Wine, Strawberry-Banana Mead, Carmenere (from 144 lbs of grapes!), Engl. Barleywine, Modded JOAM, Concord Grape Pyment.
Kegs: Choc/Coffee Stout, Saison, Dry Stout.
Bottles: Belgian Str. Dark, Dubbel, Cider X 2, Modded JOAM, RJS Pinot Noir, RJS Aussie Cab. Sauv.
Coming soon: Blueberry Mead.