Is a panel of 'neutral' experts even possible to field in this area? I feel like anyone with sufficiently in depth knowledge of both the AV1 and HEVC specs has almost certainly derived a big paycheck for years from stakeholders on one side or the other of these lawsuits.

I'm no expert, but Google having designed AV1, I can certainly imagine a world where the codec infringes upon HEVC just enough that the lawsuit fees would come out in the wash.