I tried to play Tales of Phantasia (SNES) a while back, but I ended up hating it and quitting after struggling to get through the big halfway dungeon and deciding the game was too much of a grind. I think this game would be hugely improved if the difficulty was rebalanced. Dropping the encounter rate to 50 percent or less and boosting the earned experience and money would be a great start. I found a Game Genie code that supposedly reduces the encounter rate to zero, so I'll mess around with it when I get a chance to see if I can get the ball rolling.
I saw a review today which said that there's an NPC in the game who teaches you the ability to use special moves via Street Fighter-style command inputs instead of the L and R buttons, which allows you to perform a larger number of different special moves per battle, thereby enabling some crazy combos. I had no idea about this, and it's actually what piqued my interest in the game again. You must not be able to get this upgrade until pretty late in the game, because I never found the NPC who sells it to you. Also, the review mentions that the upgrade costs a ton of money. It would be pretty cool to dummy the NPC out of the game and just give the player the upgrade for free right from the start. The game would probably be a lot easier and more fun if you learned the command inputs and experimented with combos.
I also seem to remember one of the problems with the game was that you burned through MP really fast, and since your companions are controlled by the computer, it could be difficult to conserve. I think a neat solution to this would be to have your characters automatically recover some or all of their MP after a battle, or to have them slowly recover MP as they walk on the map. I guess you could also just adjust the MP costs, although this would allow you to cast more spells per battle rather than just making it so you don't have to use recovery items as often after battle.