Unregistered jobseekers can still send resumes and cover letters through the single job "Apply Online" facility.
When you say "You can disable registration so that no other users can sign up with your site..." I suppose that neither the jobseekers will be able to register/ send resumes too, Am I correct jomarkosabel?
Well it depends upon your coding skills so I could not comment how easy it is to implement on your part. As I have mentioned, basic knowledge in php, html, css and css will come handy for this kind of modification. The theme is not encrypted and so it can be modified accordingly.
Well maybe commenting out some lines on some template files, removing the "create an emplyer accountīs radio" from the registration page and changing some "display: block;" to "display: none;" in the css might resolve, do you think itīll be easy like that?