I don't have the basic knowledge of Python.
And I probably won't ever need this kind of parametrization nor would I ever try to install QSketchMetric.
I'll stick to DrawFromCSV and dynamic library items.
Kinda implemented in a custom way, probably to suit certain custom needs.
It is not really what we expect of dynamic blocks in CAD.
Have you experience with these types of blocks or with other parametric applications?
Does that use the same syntax or methods that you are using?
To enhance something one need to be aware of its shortcomings.
And there my contribution may end.
If you are able to implement it under QCAD then I would be interested.
Regards,
CVH