Oz should do this and if the media won’t do it. Just pay for the venue himself. Bring third party candidates in to give it an air of legitimacy.
I disagree about the third party candidates. If the Oz campaign is going to go through the trouble of staging a debate like that, they should go all-in and hire a retired pro wrestler to make himself up to look exactly like Fetterman and stand there making an ass of himself on stage. He can even use a fake name like “John Fedderman” to give it some more authenticity.