I really wish they could just make HTML support

    <img src="foo.mp4">

and have it behave exactly like all other images in how CSS handles it (with auto loop, no controls). This would solve all the reasons people use GIFs in place of videos.

Like for example

    <img src="foo.mp4" style="width:100%">

should make the image occupy 100% of the width of the parent element and auto-scale the height according to the mp4's aspect ratio. You can't do this with the <video> element without an extremely unintuitive wrapper div.