Warlocks have Tranversive Steps and 3 chest pieces with these perks (Starfire Protocol, Alchemist Raiments and Purifier Robes), Titans have 2 chest pieces (The Armamentarium and Twilight Garrison), Hunters however have [u][b]NONE[/b][/u].
All other exotics specify the type of weapon that will have extra heavy ammo and allow to carry less than these generic weapon type perks (example: 6 Ghorn rockets vs 7 with one of these exotics), and this perk also increase the amount of ammo for the Sleeper Stimulant from 9 to 12 (and sword ammo by 1-2, irrelevant for swords).
I don't expect you to create a Hunter exotic this late, but at least have this in consideration for Destiny 2.
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Bones of Eao should definitely have it. As the best generic Hunter exotic, it would be the easy solution to make everyone happy. Before Bungie nerfed the crap out of snipers, I always hated how I couldn't get the max ammo for my LDR on my Hunter. It was such a good roll too...