CLI commands for exporting sets of layers and checking total number of layers

It would be very useful to have the cli-options "--export-layers=x:y..." and "--print-number-of-layers". The first one is for exporting a specified set of layers. The second one is for getting the total number of layers within a document.

Motivation: I use Inkscape for all types of diagrams. For slide-show presentations, I use html-Frameworks or LaTeX-Beamer documents. If I create "incremental growing" diagrams withtin my presentations, I mostly use one Inkscape document and define different set of layers for the single pictures I need in my presentation. Exporting the layer-sets from the gui (by setting some layers invisible and using the export dialog) each time I changed the document is not very handy. It would be much more comfortable to use the cli within a build script or make file to get all the picture-parts I need.

I also use Inkscape together with a bash-script for creating mouse cursor themes in which this feature would be nice, too. I can imagine a lot of other applications that would profit by this feature.