It's not immediately obvious which features you want to prevent the junior admin having access to. If they can add/edit/approve links, that's most of the functionality of the program.

Do you not want them to have access to the build option (in which case their edits won't be made "live") or is it the templates you're worried about? (Switching to the Perl based templates will prevent editing other than via FTP.)

It shouldn't be too hard to create a second admin script (with certain options removed and the paths adjusted) in another password protected directory.