Two blogs with same content, different layout

Our company runs a blog that needs to be displayed in two different locations. To avoid misguided targeting, we try not to publish content that is relevant to our employees at our external website. In cases where content of relevance is published to our external website, we duplicate the content and publish it on our intranet. This is why a specific blog that is used externally, but still has interest to our employees, needs to be displayed on our intranet as well.

Is there any simple way of achieving this? These are the options I can think of:

• Having two different installations use the same database. As far as I aunderstand this won’t work, as the wp_options table can only have one siteurl.
• Using iFrames. Not really an option either, because it would cause a mixup between the branding/graphics/navigation of the external web site and our intranet.
• Syndication of content. Would probably not work as we want to keep the whole blog functionality, and not just a static, limited version.
• Some form of double-posting-plugin, that will enable posting the same content to different blog installations. Would of course imply that the comment section of the different blogs are independent of eachother.
• Manual duplication of content. The lo-tech solution, but terribly tedious.

Any ideas?