I suppose most people do little more with the X-Carve than to carve shallow writing into a flat board. If you wanted to cut at more than one level or the relief was going to be more than a few millimeters, I can foresee the trouble of having to constantly stop the machine and having to manually readjust the level of a typical dust shoe/boot.
One of my interests is in “terrain”. I do a lot of visual 3D work and I have this software that does 3D rendering of CG terrains. That is what made me think so much about machining a physical one using an X-Carve. When I first discovered the X-Carve, I imagined using it to make an exaggerated 3D map of a mountainous area like the ones you see in museums. My first thought was to turn an X-Carve framework into a 3D printer to produce such a terrain additively. If you did it subtractively it would produce an awful lot of chips/dust and a static dust shoe would be pretty useless.
Most of the dust shoes on the market take up a lot of area in the X-Y space so they wouldn’t work so well when dealing with a lot of relief besides limiting your machine’s X-Y travel. Of course one always has to keep their dust shoe from colliding with obstacles. But you never have to deal with obstacles when you only make shallow cuts in a sheet of something. I like to think outside the box and find novel ways to use the machines I have. For example, just last week I used my lathe as a horizontal drill press. I told a mechanical engineering friend that and he sort of rolled his eyes in doubt. My mill didn’t have enough “throat” to accommodate the length of the long bit and chuck but my lathe has a relatively long ways. So I mounted my piece on the table and moved it back and forth to drill two holes that were a precise distance apart. Since a lathe is only a 2-axis machine I had to find plates of the right thickness to set the fixed Z-axis height that I needed. It worked beautifully. I have a manual drill press but getting the alignment precise and spacing the holes the right distances apart was going to be difficult. The lathe worked well. That’s actually how I drilled all of the mounting holes in the clamps for the Dust Dragon.
I think that a dust shoe that moves with the Z-Axis should also be useful for those common projects but it will be the only kind for projects that require a lot of relief. It also lets you easily clear the work area by simply moving the Z-Axis up for inspection or manual intervention when necessary. I can easily do that using “Gerbil Machine Programmer” because it is very interactive. Every time you put your hands on a dust shoe you risk accidentally moving the X and/or Y position while the machine is idle and that can screw up your whole project, especially if you need precision work.