I understand the complications of putting a New Game+ directly into the game's code itself, but I was thinking of an external app that just modified a save game.....Oops. I foresee a problem with this already... Vincent and Cait Sith. Since their information isn't in the KERNEL.BIN their data is overwritten as soon as you get them. So any upgrading you might have done to them would have been lost. This includes VINCENT'S KILL COUNT which is, of course, crucial to his Death Penalty working well and probably something everyone would want in a New Game+. Consequently, since we're not loading from the KERNEL, Young Cloud would have the Cait Sith's previous stats and Sephiroth would have Vincent's previous stats. Hmm. I guess an external app won't cut it.
Dang. I guess this just isn't feasible. Sorry...