There's a sort of New Game Plus patch for normal FF3 already... you can find it at ZED's site.
Why bother? I know a ZSNES
bug that works for FF6.
Do a hardsave somewhere you want to reload (new the beginning of the game, I suppose?).
Then use the load feature to frame-skip to somewhere important and die. Wait out the 'game over' screen and wait for it to naturally load your hard save. (Something like this) will transfer the Espers stats into your 'new' characters. Get 128 to each of your stats without actually hacking your rom. (Thus, a possible exploit to rom hacks which cannot be opened with those programs. As long as they have +stat Espers to carry over.)