The ASTC Westies Group proposed a system of peer based review. Check it out here. This was not the original vision I had suggested, although the elegance and broad range solution it presents offers, I think a very good basis for an accreditation system.
I saw an interesting Email from Steve Hudson on Austechwriter recently. He proposed a system based on a series of ranks, conferred on by a peer based committee, administered by a wider membership voting on the definition and maintenance of the ranking system.
You could conceivably have apprentices, craftspeople, masters or whatever. Each rank clearly describes the skills and experience of the holder of the rank. Given our current situation, this could present a useful and immediate interim solution, until a more rigorous approach is refined in the future. It may be all we ever need.
We could construct a system of education around improving lower ranks, a marketing and promotion scheme to sell our process more quickly.