You, sir, could be my twin. Every word, down to the reason for joining this forum, would have been repeated by me in a separate post if I hadn't done my due diligence and searched the forum first.
Just to reiterate a bit, though: I think this would be a fantastic addition simply because the only somewhat valid argument I've seen against it is that your "average" user could potentially see undesired results from using it. However, as soundscape points out, your "average" user doesn't even know what a command line is. And furthermore, as soundscape also pointed out, your average user is going to simply scan for and delete everything found by the registry cleaner regardless of whether they do it from the GUI or have it done automatically anyway. In other words, it seems to me that not to include this option only stifles advanced users and benefits no one. Again, as soundscape mentioned, you could easily force automatic backups with each cleaning via this method, as well. Something I wouldn't feel comfortable using the switch without, actually.