Lightning is a name you'll almost never find in English spelling. Snow is also rare: they could have used Ice, but that's severely cliche. I might say the next ally's name would be Wind: Gale would be cool but it's also overused. Another possibility would be Ocean: Cloud has only been used a few times to my memory but it's still too recent; Rain is too obvious and River has also been repeated; the only Ocean I know of is on the Ocean's 11-13 series.

Of course, I was concocting a fanfic of VII with a villain named Ocean so I may be a little biased.