Currently, autoplay is handled separately, in each compound content type by overriding params. Ideally, they should just check if they need to call play() on the child when the content is displayed.
1. All content types supporting autoplay should have a function to prevent autoplay.
2. Autoplay should automatically be prevented unless the content type is the root content type.
3. The compound content types must be able to check if children should be auto-played. This is so that they can trigger play() once the content is displayed to the user.
4. Remove all legacy handling of auto-play.
5. Consider looking at the Editor UX for this? It's not easy to understand which element will autoplay e.g. in BS?