Sweep or Thicken a non-planar surface along a vector

I have created a `parametricSurface` that I want to sweep/extrude in a particular direction (say the Z axis).
The closest I could come to doing this was to use the `thicken` function on a `Face` that I created from the surface.
However, this sweeps the surface along the surface normal (not along a particular direction).

I dug into the source to find that the `thicken` function uses BRepOffset_MakeOffset to do the thickening.
How can I use either cadquery or BRep to perform this kind of a sweep?
Is there a modification to the `thicken` function source code that can enable this?