I'm much more in line with the ability trees. Like with the merit system, only from a much lower level. I like the current naming, but having trees that branch would be nice.

Plus we have lots of final fantasy systems to work with and draw from. But let's say we take out physical levels. Now, instead of physical points, let's say we start getting, MRD points or something. When you rank up, you can go down the Warrior Path or the Dark Knight Path. If you go down Dark Knight, you learn more magic, and abilities that boost power by sacrificing HP. Then if you go down Warrior, you learn more physical attacks and tanking skills.

Meanwhile, in turns of Conjurer, you can go down Black Mage or White Mage paths, but at the same time, you're also present with options about whether to balance your elemental abilities or go solid into one element, while for White Mage path, you have options between improving your healing effectiveness or learning more protective skills.

The other option I like is that if you arm up with a certain balance of abilities and skills from other classes, your class changes. Such as if you equip a sword, and have Red Lotus, Phalanx, Rampart, Cure, and Protect, your class becomes Paladin, and then you get access to certain gear (which for the sake of things, instead of taking it off you should you remove your abilities causes you to stop receiving a bonus from it like "When Paladin: +5 VIT, +10 DEF, +100 HP"

You could also do something like the XII License Board or the X Sphere Grid, or the XIII Crysterium. Then you could buy abilities for your class using points, and then later buy more action points to use them.

You can also add a lot more class specific options.