This looks so cool.
Add an options menu to set an item's max stack and a normal player's max storage.
Add an item creation menu to create an item with same properties as other items but ability to recolor and se damage ans size and stuff.
Make it easily modable (allow guis with the tabs to have more tabs, allow more buttons to be added, etc.)
Do it naw.
doitdoitdoitdoitdoitdoitdoitd oitdoitdoitdoitdoitdoitdoitdo itdoit.