However, this brings a lot of things into question: how does range work? How far can a character move? What is melee range?
My idea is to borrow an idea from Marvel Superheroes and Fate/Spirit of the Century; the concept of zones
A zone is really any physical area the GM deems appropriate. For example, a tavern's main room may have three zones: behind the bar, main floor, and the entrance. Zones will usually be divided by either physical objects (i.e. the bar) or some amount of distance. If you wanted to be more granular and the tavern's main floor was really large, the main floor could comprise multiple zones.
So for movement, a character could move a zone and then do an action. So, a character could hop out from behind the bar and then punch a guy on the main floor. If you are in the same zone as someone, you are within melee range.
A character can also move two zones, but forfeit an action.
Ranged weapons, thrown weapons and spells would have a minimum range and a maximum range, For example, a shotgun would have a minimum range of 1 and a maximum range of 2 (maybe 3), meaning they could shoot someone in the same zone as them, or they could shoot someone in an adjacent zone. A rifle would have a minimum range of 2, and probably a maximum of about 5. The same idea applies to magic spells and thrown weapons.
Seems pretty good for now, but it will take a bit of extrapolating.