Short video as Overlay Preview in the Video widget

As the title says, I think the ability to use a short video on top of the long version video could be very useful. I'm building a video portfolio and I want to set a (kind of) big gallery of videos that autoplay in loop mode and once the user clicks on a video, it will open up in lightbox.

Right now the only way to use the lightbox is to have an image overlay, but I don't want a static image, but a short video.