It would be great if we had the option to send notification of a new issue publication to only some of the registered users. We are using OJS 3.1, and the only options are sending to all users (including reviewers who might not want to see notification of every issue) or sending to no one. We would find it very useful if we could select subsets (such as Readers, Editors, etc.) to notify.
I actually suggested something like this last summer: https://github.com/pkp/pkp-lib/issues/2561#issuecomment-306562032.