TK Ensenga not a long enough ranged overhead for you? It has more range then Chipp's dust, and out ranges Johnny's own 6H.
You could probably come up with a huge list of Johnny changes, but then only implement 2 or 3 of those changes and Johnny would be fine, in the current game. But I wouldn't want to see Johnny having better mixups, in the high/low or left/right sense. I think that would be very out of character. He's suppose to have the bare minimum tool set needed to open someone up and hit them, but have lots of ways of making that next hit hurt more and more, whether through increasing mist level, guard bar jacking, herding them to the corner, or dangerous post-combo setups.