I really do want to see a good mod for CT as it was one of the best rpg's ever made.
I'm thinking the mod is not worth the risk. If Sq/Enix decides to die or let Trigger fall to public domain, I'll be all over it.
Anyway, there are two good mods for CT I've played. One is Chrono Trigger Colosseum. It's basically the regular game, but a well-done Colosseum is added-on, with bonus battles and prizes, kind of similar to the Gold Saucer's battle square.
The other is Chrono Trigger - Flames of Eternity. This is an unofficial direct sequel to CT for SNES, and what I've played of it is very well put-together for a fan project; Most of the time, it feels almost as good as the real thing.
There's a third one floating around that tells the side-story of Magus. I've heard good things.