Remeron affects some of the same receptors that benzos do, so I doubt that one could be potentially harmful while the other wouldn't be. However, I am prescribed both, and remeron would knock the average person out who has never taken it before. Hell it makes me sleep for 12 hours and stay groggy the entire next day, and I only take 30mg, sometimes half.
Idk how you could say remeron is not nearly as strong a sedative as xanax, remeron will knock me out where as I could take 10mg of xanax and feel great, with perhaps a slight speech impediment, but it definitely wouldnt put me to sleep. Maybe it's my tolerance, but with someone who has no tolerance to either, the remeron will knock them on their ass.
To the OP: Not a good idea at all. What if this person decides to take the remeron and go out driving or goes to work. They will end up nodding out and possible harming themselves or lose their job. This is incredibly unsafe and stupid.
To Jamtastic: Great safety measure on your part. I also always look up any pill I may purchase or take before indulging in it. Knowledge is safety.