I don't think what you're describing will work (like you said, it's basically the same thing as a Publishing Portal), but there appears to be a workaround. According to this post from the SharePoint Solutions Team (apparently not related to Microsoft), you can create a publishing site, customize it as needed, deactivate the publishing feature, create a site template from it, create a new site based on the template, and then activate the publishing feature on your new site.
It sounds like this works, but is not officially supported by Microsoft. Be careful, since it may mostly work, but I wouldn't be surprised if some small pieces of it break.