In V1 we have the option to click on the version number on the navigation bar at the top. This takes the user to a page listing all the versions from which we can browse a particular version.
It'd be great if, as an end user of the docs, I can directly switch versions of a page similar to the way it works when viewing same page docs in different locales. This would save the extra navigation/browsing.
There could be situations when current page no longer exists in previous or next versions. In that case we can either show a message to the user or take the user to the root doc of the chosen version.