I was implementing the 'hist' feature in a font which maps s to long s, and it initially seemed reasonable to me to include all accented forms of s in this feature as well, but I quickly realized that this would prove rather problematic for scedilla which, apart from looking really strange would play havoc with the fonts bounding box (the form of long s being used has a descender).
I had no qualms about dropping scedilla.hist altogether since AFAIK all of the languages which use this character weren't even written using the Latin script until after long s had became obsolete.
I was wondering, though, if anyone knows which diacritics *were* actually in use at the time when long s was still used.
I'm tempted to only include sdotaccent (for Irish) and to drop everything else. I've seen long s + caron in some fonts, but those have all been blackletter faces which included long s as the base form and which, I suspect, included long s + caron simply because scaron is part of the standard windows character set.