Most of the sites on the interwiki map should be wikis; however, there
are present some useful prefixes that don't meet this criteria, and it
would be a shame to remove them (google, cache, sourceforge, and
possibly a few others). Beyond that, though, I think you're on the right
track.
David Gerard wrote:
"The InterWiki Map exists to allow a more
efficient syntax for linking
between wikis, and thus promote the cooperation and proliferation of
wikis providing free information on the internet. Sites considered
for inclusion should probably (1) provide clear and relevant
usefulness to the Wikimedia projects (2) be trusted not to facilitate
spam links (3) be free content (under a Commons-acceptable license)
(4) be a wiki (5) be reasonably developed."