Now, instead of a very coarse contour plot, labelled with emotive terms like "low", "medium" and "high", why not produce a fine grained plot with many different numerical values and then allow airlines to generate a safety case relating to the level that they are prepared to accept (if any of this is really necessary vice "see/sense and avoid", in any case)?
The Norwegian met office have a graphic showing more levels, rather than just low, medium and high. Don't know how accurate they are though.
Forside - met.no