Nothing really because the items would still be held hostage on the forums until the winner is decided in via continuing fighting. No matter where you are as long as you face the person again a winner will be decided. It may or may not require the item duel mode to be fixed to act more like a clan war so no matter what room your in if item duel mode is still activated and you go against someone you recently disconnected from mid duel it will resume where you left off. For people who quit mid duel because of reasons other than the server ghosting it will count as a loss like normal. Like in clan wars this mode should have settings that can change the "max score" or "lead by" needed to win the match/duel.

The goal here is to make item dueling safe. If this requires a few 'extra' steps needed to take as opposed to TC duels than by all means. I would rather have to take a little extra time setting up a duel than to be scammed.