I think ultimately, it would be a NO from me. When my band organises a gig where we are sorting everything ourselves, we normally offer kit share. It saves space in the venue and prevents lots of faff between bands. But it's our event. In the case of the OP, I neither want to drop my rig off the night before, or get to the festival first thing and be there all day to babysit my rig through a dozen different bands. I can certainly see the advantage of everyone using the same backline, but it wouldn't be mine!