My 3D pantograph is buit to make use of a small spindle motor rather than a router but it can also be easily adapted for use with dremel-style rotary tools.
Originally intended for machining the small wooden parts involved in model aircraft making it's more recently come into it's own as a freehand copy carver.
A variable speed spindle motor similar to mine can be found here.
The spindle motor I used has a 4mm chuck and can take a wide variety of cutters including all the dremel accessories plus appropriately sizes carbide burrs and diamone glass engraving tips etc.
So far I've used a variety of engraving burrs on aluminium, brass, wood, and plastic.
Simple motifs can be carved into practically any size project not just small ones.
I hope it gives you food for thought. The build is pretty much self-explanatory from the free sketchup plans and uses 12mm and 3mm ply, some 4mm steel rod, plus one short length of 2 x 2, and it really is a novel thing to work with.