See https://meta.wikimedia.org/wiki/Requests_for_new_languages/Wikipedia_Moor%C3%A9#Comments.
(LangCom has decided that this is not their problem at https://meta.wikimedia.org/wiki/Talk:Language_committee#Approval_Request_for_Moor%C3%A9_Wikipedia)
Possibilities include:
- Accept that the English Wikipedia is going to get screwed. This seems seriously unwise and likely to incite a user revolt.
- Create the wiki at some other name like "mos-x-deconflict.wikipedia.org" (using the BCP47 private subtag syntax is probably the least bad). This would work, probably without major changes, but doesn't feel right.
- Create the wiki at mos.wikipedia.org and add hacks to the dumpInterwiki script in MediaWiki-extensions-WikimediaMaintenance so, either only for enwiki or for all wikis mos: doesn't become an interwiki. I've written a patch for this locally, and it's similar to what we already do for Swedish ("s:" isn't an interwiki on Swedish Wikipedia because they abbreviate "saint" as s:t), but that caused problems like T177913 and probably others.
- Convert the MOS: enwiki pseudo-namespace to a real namespace (which overrides interwikis), and do something similar with WikimediaMaintenance to add an interwiki with some other name like "mos-x-deconflict"
- Someone on enwiki suggested making interwiki prefixes case-sensitive and having "mos": point to the project while "MOS:" is a pseudo-namespace. This isn't how either concept currently works, and will probably break things elsewhere
- Something else I haven't thought of?
EDIT 2024-09-09: Current working plan is outlined at T363538#10121857. Briefly: add MOS as a "real" namespace on most wikis which contain "MOS:xxx" pages which will ensure existing "MOS:xxx" links don't break. Then fix some bugs with wikibase and CirrusSearch when namespaces and interwikis conflict, add a new parser function to be able to unambiguously create a language link/interwiki when there is a conflicting namespace, and then add moswiki as an interwiki.