XMP metadata in savefig (2D bitmaps/2D vectors/3D models) for data provenance?

Hello,
Great job with MayaVi so far - indispensible!
How much effort would be involved in being able to pass optional XMP data to savefig() to allow, say, embedding in an output bitmap, SVG or .x3d file information about how the picture/model was generated? I know that PNG bitmaps support XMP metadata in iTXT sections, SVG files can be made to contain simple XML that is ignored by, say, Inkscape , and so on.
In these days of exhortations to improve reproducibility and provide data provenance, this might be a worthwhile addition. I know that XMP Python modules exist elsewhere on GitHub, for example.