Removal backstab advantage made melee combat more interesting, and same will happen to range combat. I would advocate to try even just extended range, and see if it still makes high ground desirable. Maybe add small bonus after that (+2 to hit).
It's amusing to me that when you suggest the +1/+2 to hit as a replacement for advantage some people's rebuttal is "B-but +X bonuses are not how 5th edition works" . Well, neither is advantage for height. Or again "If you start to add +1 or +2 for things it gets too complicate to keep count". Well, thank god is a computer game and you don't have to do it yourself?