This feels like its too much work to do something simple. Instead of doing a toon replacement before entering the tournament, set up an IF section that checks for equipment stats that you do not want in the duel.
I talked about listing items on baseweapon and basearmor with some other people awhile ago, maybe this may offer a better way of handling this.
https://www.servuo.com/threads/referencing-a-list.6421/#post-41737
You could just reference baseweapon as a whole then check for equipment properties that make the baseweapon not eligible to be used in a duel.
You can have the script check if different attributes or bonuses exist on the equipment, then return false if any are detected with a message telling the player they are using equipment that is not eligible. That could be heavily expanded to indicate which equipment (based on itemname) and what attributes.
You probably could design an event item that stores and saved existing equipment but if something happens to the server before it saves and someone saves their equipment before a duel then they may lose that equipment. It's safer just to restrict items based on what abilities they have.
[doublepost=1540263576][/doublepost]You can also do a layer check on the player mobile and force the players to start the duel naked

(and of course a bag check if you realllly want to make it fair and not let them sneak equipment into the battle)
OR OR OR OR
You can also have the script remove all equipment from the player mobile and put it into a bag (created by the script) then move said bag to players bank (ignoring the item limit of course) (can also use a script similar to the Account vault that lets players move items between toons and just mod that item to hold equipment)
I mean, there is more then one way to do this, the question is how much freedom/choice do you want to give the players?