Use French when no translation
As far as I can understand, nearly all Occitan speakers also know French. When there is no translation in oc, I assume users would prefer to see a translation into French rather than an English string. Can we configure MediaWiki to fallback to French?
Yes, the Occitanie is mainly in France, so occitan speakers speak French with a high probability, so it could be logical to fallback to French.
I think it's a bad idea. Of course, Occitania is mainly in France and most Occitan people speak French (an no Occitan at all) but, on Occitan wikipedia, a large part of users come from Catalonia and they don't necessarily speak French. A bit more difficult problem is also the historical heritage of the relationships between France and Occitania as France and French are widely considered as the main responsibles for the disappearance of Occitan language. So, I think seeing French on Occitan wikipedia will create harsh reactions against.
Good point. However, according to https://stats.wikimedia.org/wikimedia/squids/SquidReportPageViewsPerLanguageBreakdown.htm#Occitan , it seems that the Occitan Wikipedia receives less than 6 % of visits from Catalonia/Spain. About 5 % of edits come from Spain: https://web.archive.org/web/20150426123709/http://stats.wikimedia.org/wikimedia/squids/SquidReportPageEditsPerLanguageBreakdown.htm
No way. For linguistical closeness reasons, Catalan is a much better choice.
Written Catalan is much closer to written Occitan than for instance Czech to Slovak or Upper Sorbian to Lower Sorbian. Until 1934 most Catalan scholars considered Catalan as a dialect of Occitan.