Hi Jake,
WP Migrate Support Team here. Thanks for reaching out with your query, we would be happy to assist!
At the moment there’s no built-in way for WP Migrate to automatically upload a database export to an external site via FTP.
One possible workaround is to schedule a database backup using CLI. Kindly see our guide below:
https://deliciousbrains.com/wp-migrate-db-pro/doc/scheduling-migrations-backups-cli-addon/
However, the WP CLI integration is only available on the Pro version of WP Migrate, from the Standard license and above.
https://deliciousbrains.com/wp-migrate-db-pro/pricing/
I understand that this is half of the process that you want to achieve. You will then have to upload the backup to an external server via FTP. This is outside of our support scope, but I think there are instructions on how to do this on the Internet.
Let us know if you have any other questions.