I don't think every adc should get an ammo system, but I think a few others could benefit from it thematically and gameplay-wise.
Jinx with a really large magazine and long reload so she has to balance between her machine gun, rocket launcher, and abilities. Caitlyn with just one bullet that has really high impact. Maybe Corki, but I can't think of anything special for him.
Draven could have just 2 axes, but he can "reload" by catching an ace - he could attack twice quickly, but can't attack again unless he catches an axe or does a short reload after he misses them. It could be pretty cool, his "reload" could be more axes dropping from the skies while an audience cheers.
Miss Fortune could have separate ammo for each gun. She attacks with whichever side is closest to the target, and each side has a separate interval between attacks ( if she shot with her right gun, it would be 1 second before she could shoot with that gun again, but her left gun can still shoot - but only at targets on her left. She would have to turn to get the original target in range.). Love Tap would proc each time a target was hit by a different gun (optimal damage and attack speed comes from alternating shots - left, right, left, right). She reloads only after both guns run out or her passive movespeed boost activates. She would have to position herself correctly and move the right way to maximize her attack speed and get her Love Tap off. And, if she shot just one gun too much, she could be left in a bad position.