I've already come to the (as yet, unrealized) conclusion that there should be a standalone from-the-repo version of the WikiKit, with this being a more of a test bed.
However, I do find it so useful, that I'm putting more and more PmWiki dev notes and other notes in here.
Which really, really suggests I should not be splitting resources, and run a single farm.
Which brings up some issues, but does solve the federation problem.
Farm is not part of the Core. At least not the way I currently see it.
However, most terminology is farm-friendly, so it's not precluded.