I'm not married to the idea of an AC penalty for frenzied raging, it's just comes to mind easily because it thematically fits with the idea of a frenzy: you're so focused on attacking that your defense is lower. It does cover the same terrain as Reckless Attack, so I'm open to a better idea. I just don't know if exhaustion is the best option considering that the encounter design favors a lot of deadly encounters.
I mean, there could be a Barbarian-only version of Frenzy-exhaustion, but that would be a homebrew, and trying to balance that might not produce positive results.
***
RAW, Rage does in fact maintain if you make a ranged attack:
[Rage] ends early if you are knocked unconscious or if your turn ends and you haven't attacked a hostile creature since your last turn or taken damage since then.
Nothing in there about the attack only being a melee attack. Why do you think Barbarians get Javelins in their starting equipment?
