Redmine

It is unnecessary else. "Add watchers" in 8.0 is doing necessary.

We've created a fix that might help you:
Sending Mail Configuration plugin v0,0,1

You can do this exactly using a plugin called Redmine AutoWatch which allows you to set a role which will become a default watcher for for respective project.

Though the limitation is that only 1 role can be defined and same role applies to all projects. But closest to what you asked for as such.

+1

The reason why we would like to get this option is that when project gets into a post release/maintenance phase not much is happening there, members are moving to other projects and are not looking into it. But from time to time someone/end user may report an issue. In such case we need to make sure that "Product Support" role gets an email, for every single change. We may not rely on user entering the issue to assign it to correct project member or group.

The auto watch functionality provided by mentioned plugin would be ok, but the setting should be role setting (in redmine/roles/8/edit), not global Redmine setting.