This is mostly noticeable on throwers, but it'd be handy if slots (and weight) were automatically freed up by removing depleted ammo stacks from the ingame character's inventory.
Right now running out of ammo tends to bug out the slots so that they're inaccessible, at least with throwing lances. With bows/crossbows, it's less of a problem since you can just drop the bow/crossbow and all of your ammo automatically gets dropped.
Alternatively some sort of drop all ammo or drop all empty ammo containers button would be handy.