[xXOpkillerXx]

Your idea of variable decay is basically something I brought up in chitchat discord but less extreme; the ideal formula would be one that varies for each chart.

Let f(c, s) = a
Where c is a chart, s is the raw goods score and a is the resulting AAA equivalency.
This gives much flexibility over various chart structures and can be implemented without too much trouble. Of course, that requires some computed difficulty, hence my work on that some time ago. I'll see if I can extract some useful stats for this thread this week.

I dont think the current system is "fixable" without big changes, it simply does not account for chart structure, which it should.