I'm not quite sure why this isn't included already, since *.wikimedia.ch, *.wikimedia.cz, and museumcommons.wikimedia.nl are all included; but either upload.wikimedia.org or simply *.wikimedia.org should be added to the whitelist so that users can perform copy uploads of files on other Foundation-hosted wikis.

Yes, I know FileImporter is a thing, and I use it wherever possible, but there are a lot of edge cases that cause FileImporter to just give up and refuse to move a file (including, but not limited to, files having broken or incorrect license templates on the origin wiki that FileImporter refuses to process or correct, having any OTRS tags whatsoever in any edit of the page, having any deleted revisions whatsoever, and cases where only the current revision of a file should be moved; I encounter a combination of these for about 1/4 of the enwiki to Commons transfers that I do). Having one of those two domains in the whitelist would make transferring files a lot easier when those complex cases are encountered.