Imagine sailing in the sea like the Windwaker, but instead of landing on tiny islands and picking random treasure, the island from afar starts to appear on the horizon, and as you get closer a huge massive piece land engulfs the screen. That would be a dream! I'm not saying I want a Windwaker game but maybe adding some elements of past Zelda games would be truly gratifying.
What you said was good. I'd like to say that the dungeons were small for a massive landscape like that. Even though the open world itself is a puzzle of sorts, it does get sometimes repetitive, and it would be nice to have more themed dungeons, monsters and an engrossing Story (fix the character sounds please).
That said, I do always feel that creating a story in an open world is difficult. You either get games that focus on the story and make it more linear, or games where the story becomes secondary. I feel BoTW's story while not great, was very effective in setting the open world tone. So it would be interesting to see what they come up with.
As you said, BoTW is a marvellous game, but what's amazing is how much the series can push forward from here, and I felt that since I started playing the game. They got the harder part right, the physics, open world and all the new mechanics, the next iteration should just utilise those aspects and evolve the other shortcomings.