Plugin idea: add a little bit of javascript into Obsidian so all YouTube / Vimeo embeds automatically become fluid, now filling the full note width.
Basically inject this javascript into Obsidian.
Would be neat 
Also, some disclosure… I did ask in Discord how this could be achieved and was suggested to “Just write a quick plugin!”. I kind of tried that… or at least I tried to understand how that process would work, but I just have no idea 