I completely agree, if you decide to do it and need any help PM me. With something lightweight like this it would definitely be a lot better with a simple file system instead of a whole database that you need to set up and deal with. I have done something similar before in PHP, but the Ghost front end is really nice.
The difference between 'CMS' and 'publishing tool' is semantic. Ghost is connected to a database, allows you to create content and manage assets, and if you read through the discussions in their forum it's clear many people are already excited to use Ghost not just to blog, but to create websites.
That's not to say they will become Wordpress, but just to point out that content management is in fact part of what Ghost is created to do.