The current way the game handle classes hinders a lot the game mechanics as it makes difficult to add new unique classes.
The classes could have an unique stat to that class (Warrior: strenght, mages: maigc, cowboy: artillery, archers: archery right now)
So if you are a archer, you would only see archer stat: archery, not being able to see other classes´s unique stats.
This would allow to add tons of new classes without flowing the skill tab UI with unique skills visible for every class.
Necromancers, Priest, Paladin, Pyromancer, Aquamancer, etc.
Every class would only see their own stat class skills and perks.
It would be useful to get bank stash that allow the player to organize better their resources and class weapons/armors.
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How do it works?
Weapons are the way that currently tell what class you are using, there could be a mystic object that tells the player´s class (an orb of a warrior, an orb of a mage, etc each or would provide the player the use of the skills of that specific class orb) (could be something else instead of an orb tho)
The player starts with a single orb and can can purchase other classes´s orbs later on in gameplay.
Those are stored on the player´s orb tab (displays all the classes the player has unlocked). (It could start with 5 slots and the player can purchase new slots for unlocking new classes).
Each class has it´s own level, so you can have a warrior class level 100 but if you switch to mage class, you start from level 1 (you keep everything but your level when changing classes, each class has it´s own level, skills and perks)
You can still equip other classes armors but of course the stat are not changed and might not fit your class stats.
But you can´t equip other classes weapons. In each weapon there is a text that says "only for warriors, paladins and gladiators" for example.
This would allow to expand the game content to a new level and gives the player the opportunity to build their stats respectively to each class they have unlocked.