Here is a proposed structure for supplemental data
<scriptData type="Latn" lines="top-to-bottom" characters="left-to-right" spaces="true" shaping="minimal" usage="recommended" originRegion="150" sample="A">
as in the locale orientation element.
true if the script normally uses spaces to separate words
shaping = (in normal usage)
none if no shaping is normally needed
minimal if only minor shaping is normally needed, such as accent placement
major if glyphs normally need to rearrange, or change shape depending on context
usage = value in UAX31
originRegion = continent or subcontinent where script originated. Following the Unicode book / charts (see the spreadsheet).
sample = character with distinctive glyph that can be used to represent the script in icons (eg missing glyph)
The orientation field in a locale would only be used for overriding.