Lore reasons is an extremely lazy excuse to not add something widely requested, sure lore is important but the fact of the matter is that a majority of the fanbase doesn't care about the lore to the extent that they would support denying changing current content so that it benefits other players and allows them to get more enjoyment out of the game simply because the lore doesn't allow it. Not only that, but I don't recall ever seeing something lore related say that it's impossible to glamour white mage robes over machinist armor, I mean, it's glamour.
Plus, even if lore was the reason you can't mix armors from different classes, you can always add some new quest or something lore related that retcons that restriction somehow. I mean if we didn't have the echo I'm pretty sure the vast majority of us wouldn't have made it to level 50 and would be permadead somewhere in Tam Tara or Stone Vigil if we started restricting the game by only allowing things that are lore friendly.
Anyways, my point is that lore isn't a good reason for not lifting glamour restrictions. Most people here are only advocating for armor glamour restriction removal anyways, not weapon.