This command was already present in the plugin, though wholly unfinished and unstable.
If you want to check it out, have a look at /SeeInv . Though I don't recommend taking/adding items, as it can bug player states.
I don't have any current plans to fix the issues with the command. Currently it's useful to check the contents of a player's inventory, but that's about it.
This Command would let you look in to the players inventory