Few mass-produced products are built in the style of Grant's and
Andy's approach, because of the high craft required to cut, fit, jig up,
weld and finish so many tube and other precise joints.  In older days,
the first step in creating any product of this class was to design it
around castings, in particular requiring a minimum number of machine
setups to do the finish machining.   More recently, large fabrications
start as punched and press-formed sheet - think about any modern
stationary power tool.  Neither of these approaches are accessible, for
practical purposes, to folks building one-offs in a home shop
environment.  So folks cut and weld rectangular tube, etc.

For the last few years, I've quite enjoyed designing
and making all-sheet-and-plate fabrications, where significant 3-D
structures are created from e.g. 1/4" plate, using waterjet-cut
mortise-tenon joints and finger joints for "snap together" assembly,
typically requiring no jigging and minimal clamping prior to welding.
 Where a volume product might have bends formed using a hydraulic press
brake, my versions simply have intersecting plates with precise joints.
 From time to time, I've posted photos here, while trying not to draw
undue attention as both a group moderator and commercial shop owner in
it for the $.

The typical successful project completely eliminates
milling machine operations, and requires only lathe work, to make for
example shouldered bearing bores.  All the adjustable slide-and-lock
connections in the grinders, for example, can work fine as raw waterjet
cuts.

Anyway, these grinders could be redesigned to be
functionally equivalent, but constructed with way less labor, by moving
to waterjet-cut plate fabrication.   The cost tradeoff is up to the
builder.  Given a set of CAD files, taking a wild guess, for maybe $350,
someone could order one copy of the grinder, and I'd cut one grinder
kit, maybe 125 lbs of parts in perhaps 1/4", 1/2" and 3/4" plate, and
both parties might feel like they got a good deal.   Me doing the design
is out of the question, but if someone really wanted to do this, I'd
happily work with them to make best use of the process.

Bob
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This is Bob's shop: http://meadowcreature.com/waterjet/
And Bob at a show