The ranger's thematic gimmicks informs it's mechanical gimmicks and those are all over the place.

You have the base Ranger whose entire identity is centered around a spell that marks a target and the Hunter is the only subclass that literally does anything to modify it

Let's take Gloom Stalker for example, What if the Umbral Sight was changed so that, while you have Hunter's Mark, you can always see/track the marked target even in complete darkness.

Then again, stuff like this is one of the few ways I could imagine you could literally make all the different classes more unique with the current set-up without literally having to remake the game ans system from the ground up.