I dunno if I'd call PS3 tech demo, console Dissidia, and arcade Dissidia different designs. They've all got the same costume, facial structure, etc. the models and texture work is done to different levels of quality. Console Dissidia is the most different of the three, and even that's only really because his expressions and animations are stupid, not because of the design itself.
The ones that do stand out as unique are PSP Dissidia and Kingdom Hearts series, which are heavily stylized and not meant to match, Advent Children, which is stupid and emo despite attempting to match their normal style, and Crisis Core, which had to be different because Cloud didn't have the SOLDIER uniform yet. All of them have reasons for their differences, so it's no surprise they are further from the source material.
If they were to remake the game, I think he'd probably have the same basic costume, etc. I'd be far more worried about the game's art style itself; Square Enix has shown a propensity for those ugly FF3DS-style chibis with their remakes, and I would hate to see FF7 ruined with that look; the original PS1 game even looked better than that.
