Hacking does not fit with Battle Royale. A simpler idea would be to allow the purchase of all items for that vending machines rarity. It is only the Playground, so allowing the purchase of all items is not game breaking.

eg:

When a player walks up to a vending machine, instead of pressing the Action Button to use a vending machine and receiving an item, a new menu similar to the picture in your OP will open up on the screen. The menu system could have three options the person will need to select(four options to choose from though). The first row and first option is the type of Material they want to use to purchase the item with(all three materials will be displayed at the top, beside each other). The person can use any one material they want. The second section and second option will be the item or weapon they want to purchase(you can only select one at a time). The third option, at the bottom of the menu, is an OK or Purchase button and beside that button is the fourth option, which is a Cancel button.