Personally, I wouldn't want to play as anyone but Link. Sure, he isn't very expressive, but I always grow attached to each game's Link through the gameplay rather than dialog/story. The fact that he doesn't show any emotion also means you can project your feelings onto him and feel more a part...
I would like to see a much smaller world. I really like the idea of most of the game taking place in the unexplored areas of Hyrule (underground, maybe underwater). BotW gave you so much freedom to explore all the iconic locations from the series that it doesn't feel worth it to revisit them...