Actually in spirit tracks Zelda is a playable character alongside Link and she's pretty badass since she's a ghost that possesses evil knights and gets new powers based on what kind of knight it is.
Yknow I don't really think having Zelda as a protagonist for a game would be so out of the question. I mean in the recent games she's pretty good at using a bow and a sword, and she's supposed to be talented with magic so I can see a game where Zelda has a bow/sword as her main weapon and instead of new items she learns new spells. Hell, maybe even have the game show Zelda working behind the scenes to show just how much of an impact she has on Link's adventures.
Brianna isn't wrong that this would be an interesting idea, but you just know she's not saying this because she thinks that Zelda would make for an interesting play style in a LOZ game. No chances are she was just thinking about replacing Link with Zelda in the next game and have virtually no changes other than maybe having her in a cute outfit for John to yank his phantom gherkin to.