QwtPlotSvgItem scales the viewbox of the SVG into plot coordinates. An extra rotation doesn't make sense here by definition.

When using the SVG for a symbol ( f.e as marker ) its size is in widget coordinates and the SVG could be rotated before passing it as symbol.

When the rotation of the symbol is value depending ( f.e the z value of a 3D point ) I would implement my own type of plot item. It could be similar to QwtPlotSpectroCurve, - of course with mapping the z value somehow to a rotation instead of a colour.

Uwe