The first action the team should take to make the edits is to update email approval status1. Updating email approval status allows the team to change the status of the email from approved to pending, which enables them to make changes to the email content, subject line, preheader, or sender profile1. After making the edits, the team can resubmit the email for approval and send it to the business units.
Canceling send using email is not the correct answer, as it does not allow the team to make edits to the email. Canceling send using email is a feature that lets the team stop an email send that is in progress or scheduled for a future date2. However, it does not affect the approval status or content of the email.
Unsharing the email is also not the correct answer, as it does not allow the team to make edits to the email. Unsharing the email is a feature that lets the team remove access to the email from other business units3. However, it does not affect the approval status or content of the email. References := 1: Edit an Approved Email - Salesforce 2: Cancel Send Using Email - Salesforce 3: Share Content Across Business Units - Salesforce

An automation that imports subscriber data regularly and updates key data extensions is what NTO should create as a good first step to add automation to its email marketing. This automation will help NTO keep its subscriber data up-to-date and consistent across different data extensions. It will also enable NTO to use this data for segmentation, personalization, reporting, etc. An automation that deletes old data extensions, emails, and reports may be useful for cleaning up unused assets, but it is not directly related to email marketing. An automation that contains several recurring emails and decisioning points may be too complex for a first step and may require more planning and testing.