We need a secondary official SSVG (Secure SVG) spec so the changes can be guaranteed by browsers and other implementors.

This would allow an update to the xmlns to

    <svg xmlns="http://www.w3.org/2000/ssvg">

Which would allow the image to force SSVG mode and disable all non-approved features, but you could also update the image tag so the client could force security on potentially insecure SVGs

    <img type="ssvg" src="/insecure.svg">