I don't read much furry literature so maybe something features this, but I don't think I've ever seen a conception of a furry universe where different species/categories have differing vocal physiologies, where they would likely have varying severities of speech impediments for languages that originated with differing physiologies. So it would be unlikely to have any real lingua franca (like English and Mandarin are now), because there likely wouldn't be a single language that even the most common species could all intelligibly speak. Other than maybe a very simple constructed language (like, phonetically simpler than even 
), but it wouldn't have enough expressiveness for technical use nor formal political/business use.
