So, I came up with a few ideas earlier and they seem pretty good in my opinion.
There are 15+1 for an ultimate weapon 'Ranks' of each weapon type(Short and Long Swords, Axes, Bows, Guns, Spears and Crossbows) and there are 4 different 'tiers' of each. 1-5 is Tier 3, 6-11 is Tier 2, and 12-15 is tier 1. 16 is tier +, which represents an ultimate weapon. For instance, you find a Stick, a Rank 1 Short Sword Weapon.
It has several stats, including ATK bonus, DEF bonus etc. In addition it has 4 slots in which to put skills(known as Weapon Arts) onto it. The higher the tier of weapon, the more Weapon Arts it can hold. How do you get Weapon Arts onto the weapon? As you use a weapon, you will gain EXP for it, and when it levels up, it will not only advance to the next Rank, so a Stick would become a Dull Shortsword, but also give you a choice of skills to "Teach" it. The process continues until your weapon Reaches Rank 15, where you can choose to level it up to the the maximum possible level of 30, where it willl turn into an ultimate weapon. The skills you can teach your weapon arn't random and are determined by the character using it, for instance, the Main Character learns mostly fire and physical attacks, going from Rank 1 to 2 would result in low level fire attacks like Fire Alpha and low level Physical Attacks. Later on, going from Rank 11 to 12 will give much stronger skills.
The higher the tier of weapon, the more slots it has. Tier 1 has 4, Tier 2 has 6, Tier 3 has 8 and Tier + has 12. Tier + weapons already have 4 skills on them, the strongest form of the elemental spell used by the character who was using it at the time, and 3 special skills only on Tier + weapons, one that increases overall damage, one that increases overall defence, and one that increases overall speed. You can imagine that using an Ultimate Weapon increases all your stats by a considerable amount.
As far as armor is concerned, it's the same system, 15 ranks plus a + rank for each type. It cannot learn skills but instead learns the resistance to the "Opposing" Element that the character who has it equipped. If your character uses fire, it will get resistance to water, for instance. It's intended to help those players who, like myself forget I have specific equipment on and leave armor on the whole game. + Rank armor will completely negate the effect of the opposing element.
And now for Skill Customization. There are 10 skill "links" within each element. As I spent several hours pondering this, I quickly whipped together some names. In addition, each Skill has a Alpha, Beta, Delta and Omega version. Once a Omega Version of a skill levels up, it will level into the Alpha version of the next skill. For instance, Fire Omega would become Flare Alpha, so on and so forth until you reach Apocolypse Omega. When you reach this, you'll get an accessory that will boost your fire or whatever damage by 50%. Multitargetting skills have different skill chains even though they are part of the same element.
so yeah, I wanted a bit of criticism on this.