Why not just make the theme wide enough to accommodate the default video size?
Hmm, yeah – I guess that would work. I’d have to change the embed width as well. JS isn’t my strong suit, but I’ll try it.
As far the theme, I’m just the front-end developer. The designer is ok with the user manually changing the width tag when they paste the code in. However, I would like to make that a bit more user friendly and automated.
Just remember, your JS will need to execute AFTER any of these plugins fire (so that all the objects/embeds are already created)–i.e. you’ll probably want to execute your JS after the <?php wp_footer(); ?> tag in the template (since that tag is what sets off most of these types of plugins).