I love FF12, it is my favourite game ever and I have done everything there is to do in it and even own the international zodiac edition. I try to learn everything I can about the game and i woiuld go out on a limb and say there are probably only a few people out there who know more about FF12 than me
But god I hope this isn't true, why would they put vaan in?, he (and penelo) was only added shortly before release because Basch was deemed unsuitable as a main character due to square thinking that the reason vagrant story didn't do so well was it had a 'too strong' lead and that FF12 might suffer a similar fate in Japan (their target market with FF12 and FF in general despite all the 'westernisation' talk surrounding FF13) if Basch was left in the role.
Put in Baltheir or Fran and I will become an advocate for this game (dissidia 2), Basch would be a reasonable, albeit nowhere near as good, choice too. Dare I say it, even Ashe would be better and she is my 2nd least liked FF character after Cloud Strife (the point being here that at least Ashe has enough personality to be severely disliked, Vaan and Penelos characterisations are so weak they are only a shade better than 'choose your own generic outcome' bioware characters IMO so I can't hold an opinion one way or the other as I simply can't bring myself to care about them)
But I really hope they don't put in vaan or penelo, Even I will admit FF12 may have been a better game without them (and seeing as its my favourite game thats saying a lot) and I'm sure this version of dissidia would be too.