We currently support online streaming video from YouTube and Vimeo using the widgets in our editor. We are looking into expanding the video options with the addition of embedded videos.
It will always be a tradeoff of offline video capabilities versus large bulky download sizes, but we are very optimistic that we can find a way that works. Ultimately it's also up to you if you want to offer a 200MB size issue or an optimized 30MB issue. We generally advise staying around 50MB maximum in size.