In the version of Episerver CMS that I use, when an editor clicks Move to trash, they get notified "Any incoming links on the web to this page will not work after you move it to the trash." 
Are you saying that this warning is not adequate?
Or are you saying that editors should not be permitted to delete content?

I understand that users get this notification, but humans make errors and I think having an automated job that knows no context shouldn't be responsible for permanently deleting this kind of content.

I'd like to see a warning so an admin or a developer can make an educated desiscion whether or not this content can be deleted permanently.

Just prevent editors from moving referenced content to the trash like this

    [InitializableModule]
    [ModuleDependency(typeof(InitializationModule))]
    public class PreventDeletingContentInitialization : IInitializableModule
    {
        private IContentEvents events;

        private IContentRepository repository;

        public void Initialize(InitializationEngine context)
        {
            this.events = context.Locate.Advanced.GetInstance<IContentEvents>();
            this.repository = context.Locate.Advanced.GetInstance<IContentRepository>();

            this.events.MovingContent += this.MovingContentToTrash;
        }

        public void Uninitialize(InitializationEngine context)
        {
            this.events.MovingContent -= this.MovingContentToTrash;
        }

        private void MovingContentToTrash(object sender, ContentEventArgs e)
        {
            List<ReferenceInformation> references = this.repository.GetReferencesToContent(
                contentLink: e.Content.ContentLink,
                includeDecendents: true).ToList();

            if (!references.Any() || e.TargetLink.ID != 2)
            {
                return;
            }

            e.CancelAction = true;
            e.CancelReason = "Deleting this content is not allowed, because it is still referenced.";
        }
    }

When a page is deleted, the change is not permanent. The page is moved to the trash container and can be restored by an authorized user.

Further, to prevent users from deleting content, remove their access rights to do that. Only give administrators permission to delete content.