Their still might be a chance that Celes is a character which is why Terra doesn't have that outfit. Kefka's wasn't a surprise though. Either way, I actually like their alternate outfits.

Squall's was a bit of a surprise and I'm actually surprised how well it looks in Dissidia. It looks kinda plain in the normal Amano sketches but has more zazz in the actual model. I can't say the same about Cloud. I love his Amano outfit but I never realized how clashing those white boot were until you see them in the model. The rest of the outfit I like but not the boots. Vaan and Lightning's normal alt outfits are basically the Amano designs but like most of the designs he did of other characters after IX, he basically just changed the color scheme a bit and didn't bother with extravagant designs like he did for the PS1 entries. That's why White haired Lightning and Black leather Vaan are not that impressive cause they are basically palette swaps at best like Tidus and Zidane were.

Sephiroth's is the most disappointing for me. Mostly cause the difference between the Nomura design and Amano design are negligible. The shoulder pieces are slightly different and the few accessories Amano gave him are missing. No real big difference there. I wanted him in a standard SOLDIER uniform just cause it would be awesome to see him in an outfit that didn't have a black trench-coat or half his body exposed, but I guess SE doesn't feel like fans would accept that.