I think special shops (all of the shops with "limitless" stock) should have like a drag and drop option, like a shopping cart type of deal to buy in bulk , you grab the item/check a little box next to it, drop it into the "cart"(in case of the drag and drop thing), click a button to take you to a page confirming your purchase/telling you if you have enough sp/event currency to buy it all then click the confirm button(also appreciated would be the option to buy multiples of a single item at once kind of like what you do with the vault items).

Mostly i think this would be useful for purposes of making the buying of items faster than having to individually buy each item.