Except you can level your gear and that will fix the level cap issue, since your gear directly affects your three stats and only affect the battle score system, it's easy to grind a few levels for weapons and accessories and just plow through the games enemies if you are having issues.

Seriously BoB, you don't think I know how to see an exploitation in an RPG battle system? There are very very few systems that can't be made broken or not have ways to get past restrictions. There are always ways to get around things and FF is usually one of the easiest to bypass. If you want a difficult FF, play the NES version of FFI or FFIII, or do a challenge.

The leveling system from Suikoden is not one I would suggest for VI because manipulating stats by leveling is a core customization system and considering a characters level is actually the most important element of the battle system (most of the damage algorithm, including just the basic Fight command, use your level as part of the damage formula) so such a system would bork the game. I also feel the level cap from XIII would not work in the Ruined World segment since all the areas have enemies of similar difficulty to offset the players freedom of choosing where to go. I only mentioned I felt it was a better system than XIII's level caps as it's more user friendly.

Honestly, VIII's leveling system is probably the best idea, it just needs to be bigger and greatly retooled cause the issue with VIII's system is that the only thing that changed as enemies leveled were their stats and their magic. Since borking your own stats is pretty easy, the only stat that would bother a player is their Hp as it suddenly took forever to kill one of the dragon enemies cause they almost had a million Hp. Instead, the levels should also affect their attack scripts. Another idea to make enemies meaner is from FFIV, where enemies had counters for specifics commands. VI has these to a degree but it's pretty much de-fanged since IV's version of it. A combo of these two would make you think twice about leveling to succeed and it would change the enemies so strategy would become more important as the enemy would change as you got further into the game. Such a system would make the Ruined World very interesting as you try to revisit areas only to find the enemies have become stronger since you first wandered through.