Can I use the main Multisite as a backend only?

I need to implement an admin solution to manage a multitude of existing sites that each lives on an individual subdirectory on the same domain, with their own respective databases, users, themes, etc.

I would like to know if it is possible to have a multisite setup that would use the main site as the backend only, i.e. this main site would not have a public-facing website, and if it is possible, if it would require any special settings? With settings, I am referring to SEO, security, databases, etc.

I am aware that this would require a single database with separate tables instead of separate databases as it currently is used, but could this not be achieved using MySQL imports and exports?