Zelda Maker would be cool.

I'd love to see the crazy dungeons made by other people.

Aren't the controls too limiting? Or not the controls per se, but the mobility. Would a "Zelda Maker" work as well? Can you really do that much with it? Maybe I'm just not very creative :P

Yeah, why make ambitious games...

A Zelda Maker would require a lot of features if you want to make interesting Zelda games with it. It would be disappoiting if you only could do action-heavy or puzzle-heavy games so you'd need some kind of Monster/Boss editor, lots of different tools for making puzzles, an Item editor, etc. It's certainly possible to make but I don't know if it would be worth it.

I feel like a zelda maker would almost have to be limited to being a dungeon (overworld puzzle ala lost woods at most) maker. I think giving people the option to build in actual towns and quests is way too overwhelming and unfocused for the average consumer. If you included the overworld it would probably turn into something minecraft-esque, which we don't need because we already have minecraft.
At any rate, I see why he would say that it's a challenging idea. Mario Maker is something purely gameplay based, it gives you instant gratification. The most comparable part of zelda in that regard are the dungeons. As soon as the overworld gets involved, it gets into much more complicated stuff like story, npc-interaction, personality and such things.

Although it would be kind of fun to have a hub town that is populated by 3d Mii sprites that give you quests and such. (That ventures into MMO territory however....:/)

I'd just make an original Zelda game by itself, and have a separate Dungeon Maker mode, where you can change between styles to do certain tasks (like sometimes you'll need to shrink so you go to the Minish Cap style, then later you'll need to use the Boomerang item more freely so you switch to a Phantom Hourglas/Spirit Tracks style, then after that you'll need to get to another side of the room so you go to the style of A Link Between Worlds)