Not sure how I feel about this whole mentor thing since it usually means a lame and forced theme week. If they could do the mentor and just do the genre instead that would be awesome. I love Dolly and she would be great for country week and then have somebody like ZZTop as mentioned above for rock week and so on and so on. General gist is that for each weeks genre they pick a top selling and well respected artist that represents that area to mentor the contestants. I'd also love to see more of the mentoring, why can't that be filler instead of the lame call in or whatever else they choose?
(Of course this is all contingent upon who they can actually get in but considering the popularity of AI? An artist would be nuts to pass up the opportunity, IMO)