My 2c is that while this is admirable, I think bringing one naysayer onto the show would be hard to do in a way that is particularly useful to the community and respectful to the naysayer.
I think an updated ‘naysaying episode’ - “Keto Mythbusting 2” - which I believe has been done much earlier in the podcasts - common problems and their rebuttal (to give us all a concise toolkit to deal with the naysayers in our worlds) would be useful every once in a while but that doesn’t necessarily need a sacrificial lamb on the show.
If they are well versed in the mainstream BS they will just spout reports and the 2KD would just spout (better) reports . If it is a layperson who believes what they are told by the mainstream/medical establishment, it might just be painful to shatter their beliefs live?
We definitely need to better battle naysayers, its more a question of approach IMHO.