Hi Scota,
My wife and I used foredom tools for many years, but not for engraving. Nonetheless, there are likely a few downsides to the engraving handpiece and setup. Foredom pendant drives create noticeable torque that, to me, would be annoying for engraving, at least at first. I am sure you can get used to it. I cannot see how you can hold the handpiece with it properly nested in your palm with the thick flexible shaft getting in the way. On the GRS and Lindsay air gravers, the small flexible air hose is easy to get out of the way and the graver handpiece can be positioned in the palm like a manual push graver. Finally, the noise from the flexible shaft drive, although not really loud, always drove me crazy. It always sounded like an old dentist drill. You might want to wear ear plugs. On the plus side, I suspect that the drive can be used with different hand pieces so you could use it for polishing and grinding as well. Also, Foredoms need frequent maintenance. Usually, the shaft must be dismantled and greased every 50 hours of use.
dave