I main Astrologian and all I view this as is a bizzare QoL suggestion.
What next? Hide the Bards bow. Hide the Scholars fairy. Where does this stuff end.
I understand why they decided to let Machinists hide their barrel. There was obviously overwhelming desire for it. But this is just silly.
It wouldn't be a issue to hide the quiver on BRD, some animations don't even attempt to draw the arrow, nor do you actually ever run out because the arrows are aether or something along those lines.