Additional resizing option for playable videos in chat

It seems quite annoying how when someone sends me a facebook link or a straight mp4 file or something and I want to watch it without opening it in my browser, that the only two options are to watch it in the tiny little thumbnail prewiew window or to have it take up my entire monitor with the fullscreen button.

My suggestion is something similar to what YouTubes theatre mode achieves, where I can have it take up the top half portion of my chat feed or something while still being able to view the Server/DM chat and being able to actually see the video whithout it taking up the enitre screen.