Cool idea but there's noway they'd get all those guys together for an entire tour. A show here or there maybe. Out of all of Ozzy's solo guitarists Gus G plays the Sabbath stuff most accurately. The others have always embellished the crap out of them. All the extra embellishments that the others have done detract for the power of the riffs.
Although since they are filling in for Sabbath it would be best if they'd play mostly Sabbath tunes including some of the new tracks they're working on. Not going to be the same without Tony being on stage though, he has such a powerful presence.