I now discovered that the experience enabled through this permission is different than I would have expected: Users with this permission won't get access to the "Publishing" admin backend. Instead once anyone with full studio publishing permissions enables preview on production then those with "Preview changes" permission will get the preview forced upon them. They can tell they are in preview by the top preview toolbar element (which by the way could get some design love to be upgraded from the Lithium 2012 design).
So actually no need for a custom element or link entry point to use it.
