Well, it could also be as good as combining Marth or Pikachu with Snake or DDD. Its all about how they interpret the Zelda stuff into the fighting game mechanics. For example, Zelda uses magic, and there is no logical reason it HAS to suck so bad like it does in brawl. She could have a huge magical tether grab, a GOOD projectile, way less lag on her recovery (imagine if it was like MK's down B), aerials more like Lucas' (huge sparkly hitboxes that dont rely on a small sweetspot).
Sheik could be quick, but more powerful and switching could be made way less laggy if the other character was already loaded. You would be able to safely switch any time you were launched, or you threw your opponent had mid percents (as safe as it would be in brawl with better load times). The team would be essentially immune to stale moves.