I think I have an easy 3.3.x workaround.
- Using ACP->Posting->Smilies I can Export and download smiles.pak.
- In the downloaded smilies.pak I find and replaced all gif instances with svg.
- Uploaded all the new SVG smilies and the new smilies.pak
- Use ACP to Install smilies package, thus making all smilies the SVG version.