They're both main and support characters, though. Tetra is pure support in Phantom Hourglass and serves as no more than a plot device. She plays a good role in WW, although only partially, with Toon Zelda playing the other half. Tingle's supporting in many games, with a very small one only in Oracle of Ages, and his main roles are among his now 4 games.(I think the 4th one hasn't been released?) I don't think we need another persona of Zelda before another completely different character. That's why I like Tingle, Impa, and Ghirahim as good choices(in their own separate slot respectively). They all have very unique techniques.
That, and my main Pirate choice will always first be Captain Syrup.