I think the idea is great and I wish the organizers the best of luck. However no PA tells me it must be a very small festival or all the entertainers have very powerful voices. Further to this I would think that some musician would also refuse to accept to do a set because their voices are not strong enough with no PA. I myself could not do a gig(Celtic Group) without a PA because my voice has gotten weaker with age plus the back up musicians (6) would completely drown out my voice.
But hay!, the idea is still a good one.
Beer (adrien)