Problem: Often times closely related projects might have very different pages on a topic which might appeal to different readers. These readers don't know that this other page exists as an option.
Proposed solution: Allow projects to define a sister project (e.g. Simple English Wikipedia for English Wikipedia) and if there is an article on the sister project display a button to allow them to click to the sister project page
Who would benefit: Readers who wish to try different versions to find the best one for them
More comments: Besides the Simple/non-simple example I gave, I could also see projects that have a very close language equivalent choosing to enable this option for their readers.
