Yes, you could map a video onto a sphere. There is at least one other project I know of that is doing exactly that. You will likely have to apply some distortion to the video itself so it looks right when projected onto the sphere.
The only problem with this right now is that the video has to have a very high resolution - at least 2k x 2k, better 4k x 4k, otherwise it won’t look good in the HMD. The way we currently upload video textures to the GPU is particularly slow for large videos, so you won’t get a good framerate. We are in the process of fixing this and hopefully have a solution for 4.8. In the meantime, you can use a low-res video for development and testing; it won’t look great, but at least you’re not blocked.