I'd like to use Paste format in order to clean up pasted html before saving. Since I'm already using wysiwyg_filter I'd like to use that for a 'cleanup format'.

One use case it to prevent users from pasting base-64 encoded images from Word etc. into the html. The WYSIWYG API + CKEditor forced cleanup setting prevents most of this, but (depending on the browser?), some users are still able to paste in these images.

Could wysiwyg_filter be made to filter out such instances? HTML looks like this:
<img src="data:image/png;base64,xxxxxx" />, where xxxxxx is a ridiculously long string.