Look, we’re likely not getting another full class. We might get a reskinnng system, but I think it’s safe to at least hypothetically predict no new full classes for the sake of this discussion. In light of this and assuming for the moment that it turns out to be true, I think it’s long past due that we merge the pools of class agnostic leather and mail appearances into one unified set of options for classes of both armor types to pull from.
Plate covers 3 classes, cloth covers 3 classes, mail covers 2 and leather covers 4, both of mail’s date back to the earliest days of the game and 2 of leather’s are later-arriving expansion classes, meaning limited formal sets. Mail and leather therefore easily cover each other’s deficiencies.
Shaman, Druid and hunter are all nature-themed classes or at least nature-adjacent. Hell, hunters famously make up their tier sets adorned with the bits of various animals and somehow that’s mail, not leather.
Dressing a mail character is an abysmal affair because the shamanic 5-element concept is often a traffic jam of clashing aesthetics, to the point that I personally see a great armor agnostic set like heritage armor and think “excellent, a chance to make a mail character that looks good!”
I don’t see the downside of letting mail characters pick from the vast available class agnostic leather appearances, and conversely giving newer leather classes more options. If we’re still insistent on having lines between armor types, I think this one should be moved, in my not-even-remotely-humble opinion!