I managed to find a relatively clean straightforward way to do this. To see it working click on my webpage: http://developersfound.com/yde-portfolio.html and hover over the 'Youtube Demos' link.
Below are two snippets to show how this can be done quite easily:
I achieved this with an iFrame. Assuming this DOM is 'yde-home.html' Which is the source of your iFrame.
<!DOCTYPE html>
<html>
<head>
<title>iFrame Container</title>
<script type="text/javascript" src="js/jquery-2.1.4.min.js"></script>
<style type="text/css">.OBJ-1 { border:none; }</style>
<script>
$(document).ready(function() {
$('#myHiddenButton').trigger('click');
});
</script>
</head>
<body>
<section style="visibility: hidden;">
<button id="myHiddenButton" onclick="$(location).attr('href', '"http://www.youtube.com/embed/wtwOZMXCe-c?version=3&start=0&rel=0&fs=1&wmode=transparent;");">View Full Screen</button>
</section>
<section class="main-area-inner" style="background:transparent;margin-left:auto;margin-right:auto;position:relative;width:1080px;height:720px;">
<iframe src="http://www.youtube.com/embed/wtwOZMXCe-c?version=3&start=0&rel=0&fs=1&wmode=transparent;"
class="OBJ-1" style="position:absolute;left:79px;top:145px;width:1080px;height:720px;">
</iframe>
</section>
</body>
</html>
Assume this is the DOM that loads the iFrame.
<!DOCTYPE html>
<html>
<head>
<meta http-equiv='Content-Type' content='text/html; charset=UTF-8'>
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
<title>Full Screen Youtube</title>
<script type="text/javascript" src="js/jquery-2.1.4.min.js"></script>
<script>
$(document).ready(function() {});
</script>
</head>
<body>
<iframe name="iframe-container" id="iframe-container" src="yde-home.html" style="width: 100%; height: 100%;">
<p>Your browser does not support iFrames</p>
</iframe>
</body>
</html>
I've also checked this against the W3c Validator and it validates a HTML5 with no errors.
It is also important to note that: Youtube embed URLs sometimes check to see if the request is coming from a server so it may be necessary to set up your test environment to listen on your external IP. So you may need to set up port forwarding on your router for this solution to work. Once you've set up port forwarding just test from the external IP instead of LocalHost. Remember that some routers need port forwarding from LocalHost/loopback but most use the same IP that you used to log into the router. For example if your router login page is 192.168.0.1, then the port forward would have to use 192.168.0.? where ? could be any unused number (you may need to experiment). From this address you would add the ports that your test environment listen from (normally 80, 81, 8080 or 8088).