Thanks to NAMKCOR, I don't necessarily need to have different classes. However, I think I have to create a crafting system to accomodate what I need =\ I just have to figure out how to do that now xD
But if someone wants to try their hand in this, I can try to explain the concept better. I'll use it in the context of my game.
You have a spirit ally. It has several different stats. (Say, Flame, Aquatic, Lightning, Holy, etc) It can level up. Whenever it levels up, it gains a small boost in attack. At the same time, it also gains points called synthesis points.
In my game, I also want to break down common inventory items, such as bombs and whatnot. By breaking them down, it enables it to become synthesizable to your spirit. You can breakdown the same item several times at once. This leads the item to become "Spectrumized Bomb" x (Number of times you broke it down) and fits into one item slot.
Now, the "spectrumized" object can be synthesized, if the spirit has enough synthesis points. Each spectrumized object contains properties that can be transferred over to the spirit. For example, 1 spectrumized bomb will cost 1 synthesis point and when infused into the spirit, it will carry over its flame properties, thus raising the spirit's flame stat by 2. A "spectrumized bomb x 2" would take 2 synthesis points but boost up the flame stat by 4. The process can be repeated as many times over and the end result stacks up on each other. However, there are going to be limit caps to each stat.
Also, when the spirit hits a certain point at varied stat levels, it's possible for the spirit to "rank-up" or rather build-up (in the context of Dark Cloud 2). They also learn skills at certain stat levels. For example, a spirit might be lvl 10 but has weak skills but is balanced in all sections overall. While on the other hand, the spirit may have more advanced flame techniques because it has a main focus on the fire stat.