Hello *,
I think a closed wiki can have virtually any subdomain without creating any attention. So how about "cooker.mediawiki.org" and housing it on Wikimedia servers? Maybe Wikimedia Deutschland and Wikimedia CH have some servers ready for usage?
Sounds good to me, would be good if somebody would set that up. In the meantime I have an import of wikiversity running, on the old baach.de/phase3 address. This is an old server with limited traffic, so it better stays under the radar :-).
Cheers,
Joerg