Honestly, I don't know what I don't know when it comes to Oshkosh arrivals (only arrival I've ever done there was in a car).
That said:
Seems like they could set up some sort of online registration system where EAA could assign people arrival times. Like, plan to be over Ripon at 0900. Yeah, it wouldn't be perfect, some people would be early, some would be late, etc. But I got to think people would have rather been waiting it out on the ground at some other field, than doing the 20th time around Green Lake. The early morning was packed, but the late morning was pretty empty on the Fisk approach.
Course, heck, come to think of it, I'm saying all this from the comfort of my house, after listening to the ATC on my phone and watching the chaos on a flight radar app. I suppose people sitting on the ground could have done the same, and timed their arrival accordingly.
Wonder if the B-1 crew knows how much chaos they caused this morning when they closed down the arrivals?