We have to do arbitrary insertions/deletions from the middle, many of them. I think it is more like BTreeMap, but we need either sorting direction or rev(), and there were some problems with both approaches I tried to solve, but eventually gave up.
I see! The big issue I've run into with BTreeMap is that you can't provide an external comparator. If comparisons only require data that the keys already have, then the Reverse wrapper [1] has worked well for me.
