I’d like to see this too. I’ve used Ghost a few times for some newsletter efforts, and both Ghost(pro) and self hosted. While I appreciate that Ghost(pro) is setup and maintained as a service, there is very little visibility into deliverability if there is a failure. With self hosted, you can go into Mailgun’s dashboard and start poking around to figure out what happened, but it still takes time.
Perhaps a summary email/spot in the dashboard at the end of a delivery effort similar to campaigns in various email delivery tools (Mailchimp, MailerLite) showing any errors and the specific accounts/emails associated with them would help troubleshoot issues.