I don't really see the point. I like the characters, don't get me wrong, but they're not these big, vibrant personalities I care about. GTAV did it well I think because Michael, Franklin and Trevor were so different and, though the gameplay was the same for each of them, playing as them always felt different because they'd get themselves into wildly different predicaments and behave so differently, and it was interesting to see the contrast. Zelda doesn't really have that, I don't feel like having another character will add anything to the current formula bar being a way to manufacture variety that isn't there.
Plus, I tend to dislike dual protagonist games that are single-player. Every game that's done it, I've never felt its needed or added much. Even awesome games like Resident Evil 0; I enjoyed the hell out of it but I imagine I'd have enjoyed it just as much only controlling either Billy or Rebecca, rather than switching between the two.