Products.naked_plone
I’ve needed this for some time, but I’m finally getting around to shipping it.
In addition to making it easy to disable default Plone styles, this add-on provides an “Advanced Setup” site action. The action is disabled by default, but you can enable it in portal_actions -> site_actions. It adds a “placeful” string:manage_main link so you can access the ZMI wherever you happen to be on the site.