Starting with blocked-out volumes representing components that are working at #Minamil: a minimal CNC mill and vertical configuration, I've considered a couple of layout ideas:
Perhaps the more sensible & easier to make stiff: footprint about 14 x 20 cm (8 x 6 in)
The more aggressively compact: footprint about 14 x 14 cm (6 x 6 in)
For evidence of progress beyond CAD and hand-waving, here's a three minute video:
The telescopic axis design contributes to compactness when not operating.
Transparent panels for debris enclosure -- sides but maybe not top or bottom -- can fold compactly around the retracted axes for storage. Assessment of ventilation requirements required.
These depictions assume a Dremel-like spindle. Assuming a general-purpose tool that anyone might have or acquire for general use apart from this machine reduces the scope of what "the machine" includes. OTOH a dedicated spindle could avoid making the operating configuration taller, and get closer to always-ready a la stapler, at cost of added cost.
AFAIK the WEN 2305/7 rotary tool I've used so far represents a Dremel 395-type tool and other similar clones. It weighs half a kilogram, as does half a liter of any aqueous beverage. The machine does not include the counterweight. It includes the rigging for a counterweight, stowed inside the basic bounding box, to be set up when needed for operation. The user will provide an ad hoc counterweight as/when needed.
Companion project #Minamil develops the CNC mechanics. This project started as an aspiration to make that project reproducible from a short BoM and a laser cutter. Since then I've shifted toward thinking the working parts (that project) and the frame (this project) should remain separable for practical usability -- at cost of growing insignificantly larger than a tightly integrated unit. As a result, the "short BoM and a laser cutter" emphasis stays with the Minamil mechanics while this focuses more on improvisation-friendly cabinetry.