As for your last point, that sounds similar to what happened in Scotland's regional this year. This year's result was worth double last year's which in turn was worth double the year's before. The end result was that any band who came last this year immediately got relegated.Isn't that really the whole issue with the current system? There is no overall authority. There will never be any sort of consistent grading or rules until there is such an authority, or unless all (or most) of the existing authorities agree on a system. Is that likely to happen?
Looking at the issue from the outside, and from the postings in this thread, the two things that I would suggest are:
1. Kapitol should promulgate a rule that no band is eligible for the Nationals unless they have participated in that year's local association contest.
2. For national gradings, keep the three-year rule. But not with equal weighting. Make it current year = 50%, previous year 30%, second previous year 20%. In other words, reward bands somewhat for consistency, but avoids having two-thirds of the grading based on previous year's performances.
Don't know if it's a good thing or bad thing, just making the comment that similar things are currently happening.
Also, in Scotland if you're top two in the regional you are promoted and that has the habit of making a number of bands
yo-yo bands, up one year then back down the next. Don't think that is positive.