Well, I think the other elephant in the room is that, so far, those cover album events haven't resulted in productions most fans actually want to listen to. I suspect due to relatively little rehearsal time, all of the DT cover albums suffer from weaker performances, especially in the vocals department.
Plus, playing a few covers here and there is fine, but playing someone else's entire album makes no sense. I remember an interview where Bruce Dickinson was asked about DT's NOTB cover, and he just sorta "no commented", obviously not getting why a band would want to spend time at their own concert playing so much of something other than their own music for fans. I don't get it either, to be honest.
You know what'd be better? DT playing another band's album one song per night over like an entire tour. That way, the whole album still gets played and can be released, but fans who showed up on the wrong night don't have to sit through an entire set of something they don't really want to hear.