I'm not a master of how coordinate systems are defined. However, your "move rotate scale" constitute what's known as an affine transform, and you can describe these in WKT using a a "FITTED_CS" coordinate system and a PARAM_MT["Affine", ...] for the affine matrix parameters.
The documentation is too sparse and my time too short to figure it all out, but if I understand what you want, the result will look sort of like:
FITTED_CS["Some sort of name here",
PARAM_MT["Affine",
PARAMETER["num_row",3]
<... rest of affine trans here ...>
],
<The underlying GDA Zone56 spatial reference WKT goes here...>
]
I believe -- the documentation sucks! (or I suck at turning it up!) -- that the affine transformation is represented by a homogenous matrix, as described here: http://en.wikipedia.org/wiki/Transformation_matrix#Affine_transformations
The values in the matrix would then be given by something like: ("elt_X_Y" being the pattern. Or maybe it's "elt_Y_X.")
PARAMETER["elt_0_0", 10.0],
PARAMETER["elt_0_1", 0.0]
It's a Simple Matter Of Math to go from your description ("move here, scale this much, rotate by x") to a matrix -- each step can be turned into a matrix of its own, then you can derive a matrix that represents all steps at once by multiplying them together. Note that you want the transformation from work coordinates to the underlying coordinate system, not the other way around.
Possibly this was helpful in your quest. Hopefully someone can point at better documentation.
A final caveat!: I've no idea how well supported FITTED_CS actually is by GIS software. It's in the standard, however! ;)
Best Answer
There's a Python code example for doing this under Define Projection.