I only make System Images (using Macrium Reflect Free).
If I want just some files or folders, I Mount the Image (by double clicking it)
I don't use MS Windows System Images, Backups or File History. I find they are more trouble than they are worth and not reliable or efficient, in my experience.
Seeing as you don't want your backup drive connected all the time, maybe your users can make their own extra arrangements locally or to Cloud Accounts.
Easeus Todo Backup Free might be useful to them.