this is a tough question to
this is a tough question to me. I hosted a little workshop a few weeks ago (very informal) due to the plethora of questions I get every time I show up at a race or training group. I had about 10 people show up and from the comments later it seemed everyone had come away with something positive, which was my goal.
I don't think having a lot of fitness experience was all that important, as it seemed I was able to connect with the attendees a little better when they saw that not only had I run over 20 miles barefoot but that I was just some average schmoe and not some finely tuned athletic machine. This is something I tend to have a hard time with when I attend clinics as the instructors tend towards being pretty fit people, and while fit people tend to know something about being fit (which is a good thing), I tend to have some unintentional incredulity towards them that says "yeah that's geat, but you are already rail thin and can run a 6-7 minute mile while I'm here struggling to break a 10."
so the short version is I don't think one necessarily has to know a lot about fitness to teach barefoot running, and in some cases people may be more receptive if they are learning from someone like them (i.e. some average schmoe) instead of someone in awesome shape. "Hey, if he can do this then I can too!"
that aside, I agree that an instructor should have some extensive experience. perhaps managing all seasons (where seasons actually happen) and some "extreme" distances (maybe having runs several half marathons? most people I talk to consider anything over a 5k "extreme"). Might help to have some races under their belts, but probably not mandatory. It was very helpful during my workshop to be able to draw on my experience in winter, over long distances and in the handful of races I have participated in, as those tended to be the types of questions I faced towards the end ("what about the snow?" or "how far have you gone?" or "don't you get stepped on during races?").
One other thing that seems like it would make a difference to a class is the BFR's story. Mine to my class was about my weight loss and how quickly I have been able to recover from the stress of long runs (I was running 2 days after my marathon while my buddies from the training group all took at least a week, some even longer). An even better story would be someone who has come back from a seemingly career-ending injury through BFR. I don't think this should be mandatory, but I think people are better off shown what BFR can do than told "what I heard from some people". I told a few stories from people I've met about their injury recovery through BFR and people were impressed, but I think if I had been one of those people coming back from injury it would have really driven the point home. So I guess I would encourage people who have come from injury to teach what they've learned.
One of the things that made me so passionate about BFR in the first place was reading Michael Sandler's book, where in the beginning he describes the kinds of injuries he has come back from through BFR and it was incredibly inspiring. On the flip side, when I ran Ken Bob's book I wasn't quite as inspired as he had never really been injured like that (although that in itself is extremely impressive).
dang, got rambling a bit.