Dear Andrew, just in case you should ever run out of ideas for enhancements; As an advisor I sometimes get PDF files and recently, some CAD drawings contained layers, which is kind of nifty to reduce the clutter.

Sadly though, qprinter/qpainter seem to be unaware of OCG (Optional Content Groups, the PDF jargon for layers) at the moment, so my plea is for the back burner now. Probably in SVG though it can be done? Yet that is of a little less use, maybe…