Was chatting with BC about this earlier, a couple of notes:
- It would probably be best as a namespace, not an IW link. Relative IW links would be pretty straightfoward and could be shipped with default MW, but they might be broken (related: bug 18664 and bug 19270). Fully qualified URLs are not friendly for something like this, nor would they be quick to implement in a large-scale installation a la WMF.
- A pseudo-namespace (similar to Special: at -1 and Media: at -2) would be better than a normal one, as it eliminates chances of collisions with existing namespace definitions.