You might be able to easily embed playable podcasts using embed.ly.
Simply put, by adding some JS to your header, anytime a direct <a href link is included, on its own line, to a podcast, the js will embed it directly into your page.
Try something like this in your header.php
<script src="http://code.jquery.com/jquery-1.4.4.min.js"></script>
<script src="http://scripts.embed.ly/jquery.embedly.min.js"></script>
<script type="text/javascript">
$('document').ready(function(){
$('div.post_content').embedly();
});
An even better way is to include a podcast link through it's own form directly in your submit2 template, while still using the embed.ly script. That way, users can add the links more easily, and they will always be displayed in a predetermined spot that you set in your bookmarking_post template.
Hope this helps.