Subclass system
They kind of do exist with the types of weapons and subsequent armours you can build but I'd argue that's pretty much only for melee and ,to a lesser degree, ranger. Would love to see variety in itemisation but also maybe some add ons to the skill tree that advertises certain playstyles and power fantasies. It could be like a combining of two seperate skill trees that are the prerequisite to be able to access certain specific new subclass trees (ex. Running + Melee combat for assassin or melee + magic for the spellblade)