Zeus has pretty much one look, so I really wonder what they're gonna use for his alternate costumes. They'll most likely use Young Zeus for one of them (http://images2.wikia.nocookie.net/__cb20110715095810/godofwar/images/3/3c/Zeus.png), but that still leaves one alternate costume.
I was thinking maybe something inspired by his Grave Digger alter ego, or a Poseidon costume. I mean, if they can give Kratos a costume based on his brother, then why not give Zeus one as well? Poseidon uses lightning as well, so it makes sense. They'd just have to change the lightning's color to blue.
If they do give him a Poseidon costume I hope his level 3 will change with it. It shouldn't be that hard to keep the hitboxes the same and come up with moves for Poseidons elemental form. The one with the horses, etc.