Enhancement request: Notifications improvements - Custom Fields

My client has a relatively large number of custom fields on their requirements, and would like to be able to add notifications that are currently not possible.

One of the fields is "Business Analyst" ("BA"), with type "user". Whenever that field is updated, they need the BA whose name is in the field to be notified. This would need two changes that I can see:

1. Allow notifications to be triggered when a custom field is changed (today, the list of "triggering" fields is limited to standard fields only).
2. Allow the recipients to be selected based on the content of the fields, rather than people in a specific role (or subscribed followers).

Many thanks,

Colin