Access-Aide Version v096 has now been released. It is available via our Sigil Plugin Index as an attachment (see the first post in this thread or from my github repo:
https://github.com/kevinhendricks/Access-Aide
It now includes the ability to take EMPTY alt attributes and look up the image's own metadata for XMP AltTextAccessibility or failing that, exif ImageDescription to auto fill alt attribute values.
It will NOT overwrite any existing image alt value.