Well we did it like that for some videos. As Example we did it for Mathaka Mandira Video from Iraj. But the thing is machan we dont have time to capture frames and upload them, again post them one by one.
Since we dont ZIP our video files you can play them as you download, I mean if you download like 3% of the video still you can see that section. So you have a chance to see the video before you download the full.