As a work around, if I set readonly to null for both, and remove the once() function on the asset_id, then upon viewing or editing the data the asset_id and inbox_id will remain as the original value, but are open to user edits (definitely not preferred).
Unfortunately, if I set readonly to yes, and remove the once() function, it locks it from user edits during viewing or editing, but assigns a new asset_id and inbox_id.
Still exploring the issues and solutions though.