I reckon they just want to keep us guessing with the other characters. Even though some of them are easy to guess. This does remind me of a SSBB even though I hate Super Mario, and I dare anybody to say SSBB will be better than this
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Now, I had some other thoughts about this the other day. What if they pull something tricky and they give us Zack instead of Cloud? It's not too likely they will, but if they gave us Jecht to pair off against Tidus because they are the perfect rivals, then wouldn't Zack be the perfect rival for Sephiroth after seeing playing Crisis Core? Though, I doubt they would, as there would be a number of angry fans waiting to be Cloud again.
And another thing. This is the first time Kefka's evil laugh will make it out of the SNES, GBA version. It's not a big deal, but I wonder how they are going to switch it over to real voices?