Is there an editor that I can use (via sudo probably) that does not allow me to exit to a [root] shell?
Qualquer um deles. Você só precisa configurar e usar o sudo apropriadamente.
A página de manual do sudoedit diz
When invoked as sudoedit, the -e option (described below), is implied.
-e' The -e (edit) option indicates that, instead of running a command, the user wishes to edit one or more files. In lieu of a command, the string "sudoedit" is used when consulting the security policy. If the user is authorized by the policy, the following steps are taken:
Temporary copies are made of the files to be edited with the owner set to the invoking user.
The editor specified by the policy is run to edit the temporary files. The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR environment variables (in that order). If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor sudoers(5) option is used.
If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed.