CMSimpleCoAuthors is not thought as a "normal CMS", but as a complement of a CMSimple installation, for external authors.
CMSimpleCoAuthors is developed only for authors, they trust each other. For experts there are some options to compromise other subsites or the main website, if they have access to the backend of one of them.
CMSimpleCoAuthors is a specially configured version of CMSimple:
With CMSimpleCoAuthors, an external author can create content in a separate installation. The administrator can integrate this contents into the main website, with the plugin CoAuthors »
CMSimpleCoAuthors has to be installed in a subdirectory of your CMSimple installation. The co-author can work there in peace and quiet, the h2 and h3 pages can be used for the preparation of contents, because CMSimpleCoAuthors not produces any text files from h2 and h3 pages.