This was a potential hole nobody seems to have thought of, luckily. Just a bit of silly fun.
Chapter Five Omake
"I can provide you with several Portkeys," he said. "I believe the wards will not prevent them from exiting. If you can get one to each champion, they will be taken out of danger."
"Portkeys," said Harry. "Can you make them go anywhere?"
Dumbledore looked confused.
"Why, yes," he answered hesitantly, and Harry could tell he didn't know what to think.
"Well, can you make one to take me to the centre of the maze once I'm inside the barrier, one to send the bomb somewhere else where it won't do any harm, another to bring me back here, and then one for each of the champions?
"I'll leave them in the centre of the maze in place of the cup. That way this stupid competition might still finish without interruption, I won't have to fight my way through it, none of the champions need to trust me, and you guys can keep working on getting in, just in case."
The twinkle in the headmaster's eyes was the brightest Harry had ever seen it, and none of the others could voice any meaningful objection to Harry's plan. The only catch was deciding what to make into Portkeys, since the champions were unlikely to just pick up any old sort of rubbish lying around, even if it was in the centre.
They finally decided on transfiguring some replica Trophies, and putting the name of each champion on the base. They would charm them so that each champion would take the one with his or her name on it, leaving the others behind.
As Dumbledore and the other headmasters made the substitute cups, Harry shook his head and wondered just what would have happened if he had to do it the hard way. Of course, none of them had thought to ask why he was so willing to do this, or what he expected to get out of it.
Life debts between wizards could be tricky things, but Harry just knew having a few on hand, including one for a famous international quidditch star, could be only good.
A/N That's the end of the 'extras'. Thanks for reading.