There is a bug with Skript's Inventory click event (cancelling it) that you did not attempt to fix, so it is easy to get illegal items.

(Remove event-item from player's inventory) after cancelling it, since u can hotkey it to a slot.

Also, you have two "every one tick: loop all players:" lines, which, if used on large servers causes insane lag.

not only is this quite poorly coded (e.g. repeated events, no permission for command) its also pretty useless and not customizable in game at all