Should questions about other Italic Languages that are closely related to Latin like Faliscan, Umbrian, and Oscan be on-topic?
On Japanese.SE we admit questions about Ryūkyūan (linguistically related) and Ainu (not related). They don't have any official status, but if they are good and valid questions, we won't close them.
I usually like to be inclusive of borderline questions (if they are good questions). We could opt to do the same and be inclusive of questions about sister languages of Latin. We don't have to give the languages any official status, but we can allow them to form a small part of our ecosystem of questions (by not closing them).
Faliscan might as well be a dialect of Latin (if we take the old maxim that a language is a dialect with an army). Oscan and Umbrian are very close to Latin, and the overlap in specialty is nigh complete.
There are other languages which may prove useful to ask question whether we want Latin-related discussion on them or not, including Etruscan, Gaulish, Greek, and Hebrew.
Just as a couple of examples, the relevance of the Greek language per se becomes especially clear when we remember that Horace and Catullus translated Greek poems (as well did Andronicus whose Latin translation of the Odyssey is the earliest Greek literary work preserved even in fragments). For Hebrew, the underlying structure of ancient Hebrew can affect how we read the Vulgate. And for Etruscan, Latin language absorbed so much of the culture that it's brightly illuminated by the study of the language. What really counts as off-topic with these?
In my opinion, Hebrew should be off-topic unless it directly relates to Latin (basically only the Vulgate and some post-classical stuff), while Etruscan is perfectly acceptable. Since nothing further is known about ancient Gaulish, where it might overlap even a little bit with Roman culture, we should consider it. So 1st century BCE dedications in Gaulish should be on-topic. Things get trickier with Greek, but maybe we should disallow questions about Greek for the sake of Greek, perhaps to force even a tenuous connection to Latin?
And here is our first test case concerning Greek: https://latin.stackexchange.com/questions/538/how-does-the-prefix-hyper-explain-hyperopia-farsightedness