I'm with Zayk on this one, which is why I'm thinking of one of the larger/better supported South American languages. I think our four options really are Quechua, Aymara, Guaraní, and Mapudungun, and of those it was mentioned how difficult it was to find resources for Guaraní.
Personally, my votei s for Mapudungun, but I'm fine with whatever y'all pick.
“Alice locks her signed copy of the book in the chest with her lock. She sends the chest to Bob. He slaps his lock on it, and sends the chest back to Alice. She correctly interprets this as a big middle finger from Bob, and takes a chainsaw to open up the chest and get her damn book back since he obviously doesn’t want it.”