I think it could happen.
For this, I'd actually be in favor of understudies over pre-recorded voices. This is live theater, not a childrens' costume character song and dance revue. It should all be live and spontaneous.
That said, I think that each performance should have at least one anchor performer, like Steve, Bill or Eric, to shepherd the production. Of course I'd prefer all the original performers, but that really doesn't seem feasible for 8 shows a week. Not even for a limited run. The technical aspects of such a show would prove to be a feat for even a young performer.
Anyway, I'd love this to happen. Maybe they can do limited stints of this every few years. Like a special treat for faithful fans and general audiences.
Those are my thoughts.