I'm against over-leveling myself. Its funny how many times I run into people who say XII was too easy and come to find out that they power-leveled really early, and had a Lv. 99 party before getting to Archades. :rolleyes2

It can be fixed pretty easy if the monsters require strategy to win. An easy way to get this effect would be to lower gil and exp. that monsters give while jacking the price of items through the roof. Not to mention making certain useful items unavailable until near endgame (like ethers). We could also bring back tents and lose the save points ability to restore all health.

As long as the monsters were pretty powerful and used the same level of strategy against the party as you have to in order to beat them; then it will make grinding quite difficult for all but the people who seriously have no life or want a real challenge.