I have to agree with Hero999.
The exercise of vetting such "authoritative" members alone is fraught with dangers on all sides.
Who is competent (in the legal sense) to assess this? Aside from the various classes of licence, this is an international forum.
Even presuming you could find someone suitable for that job, as soon as there is any sense of formal competence being offered - you are taking on the liability that comes with it. That, in itself, is a scary proposition, but this (a forum) is one of, if not the, worst platforms to execute.
Supposing you got this far ... you still have the fundamental problem of communication via a forum environment. This is something we already have big problems with - and a significant part of that is the unknown which is the person seeking advice. There is so much in this can of worms that it is impossible to even scratch the surface in a single post like this - but you could have someone who can safely measure a 10KV high energy power bus - or someone who could blow up a "D" cell. As it is, we have run around in circles trying to cover safety and functionality aspects ... this thread is a classic.
The next step is the obvious one - actually communicating the necessary information. I won't go into details - you know how problematic this could be.
The last point I will make is, I would argue, THE most critical consideration. When the advice has been given and the questioner embarks on the journey to act on that advice, they are going to attempt to perform a task without any physical monitoring of their work. A tradesperson with a licence, has gone through specific training that encompasses the whole field. They have had to pass tests including practical tasks.
I'm not saying that we need to do that here - but I AM saying that those safeguards just don't exist through a forum. You can never say with absolute certainty that someone has followed the instruction correctly. Even photographs aren't adequate. You can't beat the mentor being in the same room as the student.
I also agree on the ban being a bad idea.
As messy as this thread (for example) may have become, it does send a message or two which includes functionality, safety and the diversity of members.