Don't use SUDO for this. Instead, add hosteditor into a group, and delegate write access to that group, using POSIX File ACLs. Look up http://linux.die.net/man/1/setfacl for a command for managing the Access Control Lists, and http://linux.die.net/man/5/acl for the actual write-up on ACLs under Linux. This assumes, of course, that you are using a filesystem and authentication system that support POSIX File Access Control Lists. To ensure that the permissions remain applied, you would likely want to delegate the application of the ACL to a configuration management tool. Puppet can do POSIX ACLs (see https://github.com/dobbymoodge/puppet-acl). CFEngine can do this (see https://auth.cfengine.com/archive/manuals/cf-manuals/cf2-Reference#acl), and I am sure Chef can, as well.
The other option is to provide a command or service that the hosteditor can use to generate the /etc/hosts file from a database/spreadsheet and a template. This would increase flexibility and enable you to put controls into the command or service.
I am sure there are other good ways to solve this as well, including a separate DNS instance (or even a separate DNS view, if using BIND9), and giving the hosteditor account the ability to add and remove records using the NSUPDATE command (see http://linux.die.net/man/8/nsupdate)