General Combat Ideas

1) An item or general ability (That is toggle able) to lock onto other entities or players. If its an item I would make it moderately expensive, but not too expensive.
2) Weapon Classes: There would be different ranges of weapons, from classes of One Handed, this would include short swords or light handed weapons such rapiers, knives, etc. The next class would be Curved: Weapons such as a scythe or a sickle would be in this class. Two Handed would be the next class (And probably the largest), including various weapons from a simple Long Sword to a semi swift Katana. Final class of weapons would be Ranged, including bows to guns (I made another post on more specifics of the gun).
3) Skill System: Pretty self explanatory; its a system of skills that can be leveled up by the player, and is almost always in a good RPG game. Some unique skills that could be in here is Duel Welding (Please don’t refer to SAO), and other stuff that you could possibly think of. (Though Duel Welding might be common in RPGs, I just haven’t seen it in a legitimate one)
4) I was going to put something similar to 3D maneuver gear in here but then it would be so much like Attack on Titan in game. So I am going to say about different armor types. You have plain armor, which is like generic clothes or leather armor and jackets (This armor would have the availability to be customized in different patterns and etc.). Then you have plated armor, which is like a casual Knight Armor, but can be made of different materials instead of iron or whatever the ore equivalent (This armor would also be the slower one). Chain mail armor is armor that was wore in the dark ages, and personally it would be the middle ground between Plain and Plated. Its more agile than the Plated Armor, but not a agile as the Plain. It is however stronger than Plain, but weaker than Plated. It also has the custom ability of both (As there were cloth symbols on the chest of the wearers). These armors could also be combined to create semi strong fusion pieces, Like chain and plated would make a moderate walking speed with good armor.