A Victorian Horror-themed Zelda. All the other major console outings have had 'themes' of their own that lent them a unique aesthetic- Feudal, Pirate, and Western... We'll see what Skyward Sword brings.
Would certainly keep Link without too much aesthetic change. Ganondorf I'm not so sure about, but if he was there I'd want him to be 'Frankenstein' themed with stitches, a huge beastly muscled body and bolts driven into his neck/shoulders. Not that he would be stupid; in fact just as eloquent and sinister as the original Creature (which is very if you haven't read the original book).
I pondered earlier about an expanded role for Epona in a future Zelda. Not only would she become playable separately for puzzles and the like, but you would gain some way of communicating with her (you could in Twilight Princess but she didn't have much to say except she knew the Wolf form was you) and learning the true depth of her loyalty to her master. This Epona is more intelligent and emotional than most horses and eventually gains wings for air travel.
Atmosphere has always been an important aspect of Zelda, much like a franchise it's been compared to, Kingdom Hearts. A scene reminiscent of the latter that would serve as a catalyst for unleashing the Master Sword/unrelated sword would be Link being tracked down and cornered by dark creatures on a storm night that materialize endlessly from the fog. His normal sword is absolutely useless against these creatures, and he runs in a panic into the church/Temple of Time to save himself, his expression clear that for once he is genuinely frightened for his life. In fact have several moments in this game where Link is terrified, perhaps too much to even draw his sword- the 'horror' part of Victorian horror. Maybe the first time he sees 'Frankendorf' up close he has a breakdown.
I loved Twilight Princess' expanded move set and would want to keep it going along with Wind Waker's ability to steal and use your enemies' weapons. Not just melee, but anything a humanoid enemy uses you can take and use for your own. In general there should be a greater variety of items and weapons you can just find by exploring the vast wilderness- another main element of the series but it loses some appeal when all you ever find when exploring is Rupees you don't need and the occasional Heart Piece.
Plotwise, I wouldn't want to make a carbon copy of the previous incarnations but the formula is already so set that adding too much might hurt it. Begin with Link accepting a mission in his city, a request by a nobleman's daughter (maybe Zelda, maybe not) to kidnap her from her mansion due to her suspicion that her father is... no longer her father. This kicks off the 'being stalked by shadow creatures' part once you escape the mansion.
