I'm referring to something like the Spiderman PS4 skill tree, where you can customize your character. Keep the experience system, but replace it with a skill point system. Consider this scenario:
You get a shotgun weapon, similar to the executor, and you have three alternatives after you reach a certain point.
More barrels means faster reloading.
Electric stuns, scorching, and other status effects
To act like a machine gun, use full auto mode.
It would certainly allow for greater customization and strategy in terms of play style.