If I could change anything, I'd tune up the graphics, add gyroscopic controls, and rererelease it on the 3DS. Wait...
But seriously, I think the 3DS remake was everything I could possibly have asked for... And a Shiekah Stone. Because some people don't have Google? That aside, I think adding or changing anything they didn't address in the new version would fundamentally alter the game on a level I don't want to see unless they're literally going to reconstruct the game from the ground up.
If they were going to do this, I think they'd need to build a new engine, build the graphics on that instead of just retexturing, reimagine the world with all of its iconic locales, but expand upon each one until it's at least the size of Twilight Princess, add more optional content, rescript the story, record voices for cutscenes, and redesign the dungeons to keep their theme, but create new challenges and puzzles along the way.
The biggest problem with this is that if they're going to make a new game from the ground up, why wouldn't they make a NEW game? For this reason, I struggled with LBW, as the world was too familiar from years of playing LttP. Don't get me wrong, it's a great game, but I would have liked it twenty times better if they hadn't copied and pasted the entire damn map. This is also the reason a Gameboy remake of the original Zelda turned into Oracle of Seasons. I think if they're going to do that much work, they should just make a new game.