Lots to think about. Wow.
OK...
Well, I think this would turn out to be a huge affair. They might consider it their one-and-only such tour. Sort of a 'thank you and farewell' gift for the fans. And maybe also to prove that they could do it. Why not go for broke and do it big-time?
Sure, I think there should be sidemen. The usual suspects would be nice: Keltner, Voorman, Cooper, maybe even Clapton. Guest stars could be added in at random along the way.
I don't see why a small orchestra shouldn't come along. A lot of songs would require strings, horns, etc.
I envision something like three separate sections - or 'acts' if you will:
1) The first section could just be the four 'lads' doing their thing as a group. Pure and not over-produced. Do a lot of the older stuff - although wouldn't 'Come Together' be a great opener for the evening?
2) Solo material. Each member gets a few songs, either from The Beatles or solo career. The sidemen gradually come out in support. Other members take turns getting a 'tea break.'
3) Pull out the stops. Full orchestra, guest artists. Do the 'tricky' stuff - ex. 'I Am The Walrus' etc. Closer? 'The End' of course.
Fun to think about.
George needn't worry. He had plenty of good Beatle song to add to the gig. Same with Ringo.
Sadly, I don't think I'd go to this concert since Paul can't sing any more. It's depressing watching vids with him these days. I wonder what the others' voices would be like today?
Maybe I'd go just to see the spectacle of it.
Set list? That's a whole other ball of wax. My brain hurts already. I'll step down now, let others suggest that, and prepare to be bashed over Paul having lost his voice.
Cheers!