Hi all!
I would like to suggest approving Wikipedia in Balinese https://incubator.wikimedia.org/wiki/Wp/ban at ban.wikipedia.org. The Incubator wiki has had a lot of activity, with more than 1,300 articles – of which a random sample looks very promising. The most used messages and more have been translated https://translatewiki.net/wiki/Special:LanguageStats?language=ban&x=D, and there is steady activity https://incubator.wikimedia.org/w/index.php?title=Special:RecentChanges&&limit=250&days=20&testwiki=Wp/ban in Incubator.
As for experts, I think it would suffice to contact someone in Wikimedia Indonesia to confirm this language – it is, after all, a relatively well-known language, at least in the region, so it should be an easy task for them to confirm its validity.