I don’t think you can “stack” html widgets behind each other. One loads, plays, then gets replaced by the next, which has to load first. I think you either have to live with the load times or drastically make changes to your content by figuring out what can be cut or sized down.
Like you have a big image and only one little part of that is animated you can isolate that part. 50% jpeg can in some cases look not too bad either. Or break items up like when you have a big PNG frame with nothing in the middle. If you isolate the borders of that frame and put the parts back into Hype you can have a significant reduction in size.