Yes, I have seen something like that, but I cannot find the photo/web site/youtube video.
It was a blue machine with yellow X- and Z-axes, and I seem to recall that the "base" was a large rectangular "box" and the X- and Z-axes were suspended from the top; I think it was made in an Eastern European country. [And yes, I do have an odd way of remembering things....]
ShopBot does something like this only with a flexible hoop-like device.
And, last and most certainly not least, its a great idea, and your drawing is very detailed and descriptive, and shows a lot of thought.