FetchCharacterApplyStatusData(Character, Status) is the bread and butter of any mod that wants to accept or deny incoming statuses depending on certain conditions. Would it be possible to add 'Source' as an optional third variable? The same thing did wonders for CharacterApplyStatus a few patches back.
Because CharacterGetStatusSourceCharacter only works after a status has been applied, I have to get creative (granting 'caster auras' to mark which turn it is, applying invisible caster statuses from every surface) and rely on methods that can prove somewhat finicky.