Wishlist: Add OpenRaster or subset to importable filetypes (UniConverter)

At the heart, a common implementation of .ora is merely an archive with a PNG thumbnail, PNG layers in a subdirectory `data`, a plain text file containing the MIME type (image/openraster), and an XML file that looks a little like the following:

<image h="1080" w="1920">
    <stack>
        <layer composite-op="svg:src-over" name="Top" opacity="1.0" src="data/000.png" visibility="visible" x="4" y="8"/>
        <layer composite-op="svg:src-over" name="Middle" opacity="1.0" src="data/001.png" visibility="visible" x="15" y="16"/>
        <layer composite-op="svg:src-over" name="Bottom" opacity="1.0" src="data/002.png" visibility="hidden" x="38" y="42"/>
    </stack>
</image>

(and <stack>s can be nested to form subgroups.)

You might notice the SVG namespace in there. "But I thought this was Open_Raster_?", you say. Yes, but there was a powerful compositing spec in the works coming out of the SVG.
It does not seem widely adopted; neither browsers nor Inkscape renders (unless a newer version than I have does) this correctly, for instance: https://www.w3.org/TR/SVGCompositing/examples/clip-to-self-examples.svg
Perhaps that is because Filter Effects also has compositing, and in Inkscape FE has all the modes equivalent to those ORa supports. Anyway, even if only simple alpha compositing is supported, I still think this wishlist item would be worth it, for no small reason that it is uncomplicated to visualise implementing:

PNG import is already implemented. As is transparency. As are groups and layers. As are IDs and labels for objects. That is basically the whole file to import right there.