While I personally would have preferred X, a Zero, is fine too.
Though, if it was up to me, it would be RMZ-style. RMZ-style Zero could basically roll right along with Cassharn, since they're both fairly sleek, smooth killers.
Plus, maybe they could have him channel a little bit of Omega into his Level 3, and make him do Omega's version of the Shun Goku Satsu.
EDIT: ON THE OTHER HAND!
...As people on the SRK post have put up as a suggestion, it may NOT be Zero we're thinkg about, but instead "Zero Gouki", the Giant Akuma robot from Cyberbots.
He WAS on the proposed character lists, right along side some of these other picks, like Joe the Condor and Ai-chan/Yatter 2. So, it may be too early to celebrate just yet...