Yeah, I think it's important to differentiate between a stage that's just a platform for the artist to walk on (which can be assembled fairly quickly and without too much difficulty), and the custom staging that you get in big productions where there's a whole world underneath.   Using the Eras tour as an example the stage extending out into the stadium field has all sorts - lifts that go up or down - down most importantly as this allows performers to enter or to leave the stage as needed. There's passageways to get from one part of the stage to another. There's what are effectively dressing rooms set aside for costume changes. There's spare instruments (and techs to look after them) so if something goes wrong above they can be swapped out in the space of seconds. There's even a track and dolly system running the full length of the stage so that Taylor can be moved from one end to the other faster than she'd be able to walk.   I don't know the specifics of the Madonna tour to the same degree but my understanding is that a lot of the same techniques are used.

Wow just got myself some Megadeth tickets and not sure I can afford another set of tickets for another gig so soon but we'll see. Fingers crossed

Can't speak for Dua Lipa's, but Coldplay's was vastly scaled down compared to their stadium production staging though, and tracks were adapted to reflect that. MOTS tour had a full walkway 30m out to the B-Stage in the middle of the crowd, and two C-Stages. Glastonbury didn't accommodate that at all and just had a very small walkway in front of the Pyramid stage, and (IIRC) a disconnected B-Stage.   Which re-enforces my point. Acts can adapt their stage shows if they really want. Most do, some don't want to. Glastonbury might miss out on the odd act that doesn't want to slightly adapt, but so will most festivals.   

Most excellent news.