I briefly browsed throught this but lately I've been paying FFXII and I loved XI now I do not believe they could achieve this in this game with out possibly pissing a lot of people of but.... Something that could change "jobs" Square enix kinda (very lightly/breifly) did this in dissidia with a couple of characters but make it connected to Block and down or Triange Circle Square at once switch to next job.... Use more basic Jobs and hell you could actually make the rank up system more useful than editing your profile options. Balanceing maybe difficult but hey so far this a very balanced game... Also Dissidia Balanced out Sephiroth nicely so it's possible to balance him.
It will be either Cloud (first on ps1) Tidus (first on ps2 and getting HD remaster) Lightning (first on ps3 and has two games and upcoming thrid) Noctis (has his game upcoming). Though from th eword most Jrpg companies don't want their characters in a brawler. Atlus is one of the exceptions and has given a greenlight for a character. Square Enix may not allow a character in due to the fact they have dissida and that since FF fans are so diverse and split into their own games. If we had a FF7 character all the 8,9,10,12,13 fans wold be upset. Since SB doesn't want to double up on characters. or we may probably see a character, level, and mash up of all different games. guessing that it would be lightning, noctis (one of the ps3) for characters as they be easier to desgin as they have solid designs on ps3. do a FF7 main lvl so one of the sectors with a view of shinra corp or ff8 garden. then the mash up would be in another level with an iconic summon from one of the games or the things from FF7 advent children. also they could make items like phoniex down where you pick it up and for like 3 seconds if a super hits you instead of killing you it saves ur butt.
this is me helping