Probably not the first person to say this, but I'd like it if they brought back traditional Zelda dungeons into the world. I know BotW is something original, and strays far from the Zelda formula (although some might say otherwise), but I think they could use the massive world in BotW to make a non-linear Zelda game. Although I'm not sure how it would work with the lore, it would be cool to go back to something like three dungeons where the world is in State A, followed by 5 dungeons where the world is in State B. Whether it be child link vs adult link, light world vs dark world, or something new altogether, I've always enjoyed that style of Zelda progression. It makes the journey seem epic when you reflect on the adventure you had.