This can acually work
But it need a format
Lets say :
Player 1 : /duel item (name of the item)
Player 2 : /duel item (name of item)
Player 1 : /duel item confirm
Player 2 : /duel item confirm
Note : if the player doesn't own the item or the item is untradeable or the other player don't have enough qi for the item it need to show some warning message
And the item shall be untradeable untill the duel is over
Devs will have some work to do but If they will add such a command i'd say yes for the idea.