I would love to have the options on video embeds from YouTube and Vimeo built into CMS. For instance these are embed options for YouTube:
This would be big for me. The one I would specifically find helpful is the ability to turn off suggested videos and player controls.
Autoplay video!!
I would prefer to be able to simply upload videos as assets, so that you can use transparent videos or motions graphics without making them background images that have no options or controls.
There are loads of parameters for YouTube (and many for Vimeo) – autoplay is one I use a lot, usually by manually adding: ?autoplay=1 to the end of the URL – but I agree the ability to do this via a simple checkbox would be helpful.