The proper solution would probably to add a function like \embed-image which
makes use of the SVG <image> tag. But that one only specifies jpeg, png and
svg. This means that for any other format it is the choice of the viewing
software if they want to support it.
this is why IMHO, for svg backend it would be even better to have a function that adds inline svg.
IIRC there was, in this ml, an attempt to create it, but I can't find the corresponding message.
Anyway, I would like to avoid conversions and, at the current state of art, I think that a way to work-around is to draw a rect with the img size, and replace it with inline svg through some external utility.