Using WebP as a background image in SVG

So I would like to do the same, or similar, to what I would do in HTML:

   <picture>
      <source type="image/webp" srcset="my-image.webp">
      <img src="my-image.jpg">
   </picture>

But, obviously this won't work:

   <svg>
      <picture>
         <source type="image/webp" srcset="my-image.webp">
         <img src="my-image.jpg">
      </picture>
   </svg>

I could use .htaccess approach, but I would prefer not to because of the 302 HTTP redirect.

The solution also needs to work without any JavaScript trickery...

This is what I ended up doing, thanks to the input from Robert Longson:

    <foreignObject x="0" y="0" width="100%" height="100%">
      <picture>
        <source
          width="1180"
          height="500"
          type="image/webp"
          class="lazyload"
          data-srcset="http://satyr.io/1180x500?2&type=webp&text=webp@1x&texture=graphpaper&delay=2g 1x,
             http://satyr.io/2360x1000?type=webp&text=webp@2x&texture=graphpaper&delay=2g 2x" />
        <source
          width="1180"
          height="500"
          type="image/jpeg"
          class="lazyload"
          data-srcset="http://satyr.io/1180x500?2&type=jpg&text=jpg@1x&texture=graphpaper&delay=2g 1x,
             http://satyr.io/2360x1000?type=jpeg&text=jpeg@2x&texture=graphpaper&delay=3g 2x" />
        <img
          width="1180"
          height="500"
          class="lazyload"
          data-src="http://satyr.io/1180x500?2&type=jpeg&text=jpeg@1x&texture=graphpaper&delay=3g"
          alt=""
      /></picture>
    </foreignObject>