I considered this, but it doesn't add much value for my primary use case (landing page).

While doing this I've learned that one can embed a <script> tag into SVG so this can implemented this way. Scripts run if the SVG is added to the page with <embed> or <object> tag, but not with the <img> tag. This opens a possibility of "graceful degradation" where the SVG uses live streaming where possible with a static fallback.