Maybe each Guardian’s abilities manifest in different ways, like as if the supers presented in-game were simply a single possible form of the ability?
Like a Titan Striker who, instead of having the Fist of Havoc ability, can channel the arc energy into a flying 50-yard punch
Or a Hunter Gunslinger who has a flamethrower instead of a Golden Gun
Or even a Warlock Voidwalker who creates a vortex that literally sucks anything nearby in
And what if the damage type (Solar, Void, Arc) a Guardian does is influenced by their individual personality? Maybe a hot-headed, short-tempered Guardian would have Solar-based powers; a calm, observant one would have Void-based powers; or an energetic, quick-witted one with Arc-based powers