That could work quite well - sort of a b-stage all the time.
My only bit where I am unsure is because of my last time seeing them in concert - Charlotte for Vertigo (2nd pass through the states), I sat behind the band somewhat high up, because when we finally figured out how they were actually handling sales, that was what was left. It was a great show (and I am glad that I got in), but they were playing it primarily to the folks across the arena from us. I think Bono and Edge looked up (practically straight up) and acknowledged the folks in our area a handful of times during the show. I don't blame them, but it was a bit disheartening to be behind them.
My concern is that with a "theater in the round" approach, then they are looking away from you more than 1/2 the time. They could probably make it work, and we would all be a lot closer to the stage. I guess if Adam is playing to one side and Edge to the other and Larry's drum kit spins around from time to time (Vertigo?) then it could be a great show. It might actually be better, if no one can really say that they were behind the band.