Our dev group versions our styles. A small change between style versions can cause numerous changes in a single file making peer reviews more difficult than they need to be.
My suggestion is to add an Format > Styles > Actions option to add style stamp. Implementation would be adding a comment with a style/version stamp at the top of the file when a format is applied. If the comment exists prior to formatting, that style will be used by SQL Prompt regardless of selected style. If the style/version is not found, the selected style is used. To change which style to apply, dev simply removes the comment before formatting.
Formatted with supplied Default
/Formatted by SQL Prompt using Default/
Formatted with custom, versioned style
/Formatted by SQL Prompt using My Style 1.1/