Keep Inventory Slot

hello again,
I would love a plugin to be create which is capable of keeping the first item in your inventory the same throughout worlds, therefore it would need to be compatible with multiverse inventorys. The item should be impossibe to take out of your inventory as I will use it as way to access a menu.
Idea for commands : /add (item) (slot)
Idea for permissions : (this doesnt apply)

 

You could look at my plugin Bukkit GUI Lib. With this plugin you can create "hotbar gui's" which are just items in the hotbar the player can't take out/remove and you can assign a command to the items when the player right clicks with them (for example /showGUI <guiname>). You just need to create a hotbargui and use
/bindHotbarToWorld <hotbar gui name> <worldname> (for every world) which makes the hotbar gui appear in the specified world automatically. Just look at the tutorial on the plugin page (it's with english subtitles!).

 

I am planning to work on a similar plugin... But why would you want to have it cross worlds? Can't players just switch out the items and go back and forth to switch it to a different world?