If there is an idiom that Piraha commonly use to talk about things outside their experience then Daniel Everett is being very misleading in the way he talks about them.
Maybe Inner Stickler could invent something? If his innovation caught on, then that would change the language.
Inner Stickler, I disagree a little bit with your statement that “As far as I know, no attempt to teach an animal language has come close to meeting even a few of these standards.” There have been a lot of attempts to teach primates language. Some of them have come closer than you think. Take a look at the article “Apes with Apps” by Ken Schweller in The IEEE Spectrum (or Google on “bonobos”, “apps”, or “Schweller” for other articles) for some more recent experiments with bonobos that seem promising. Maybe this should be a separate thread since it’s wandering off the topic. Actually, we have done threads about this several times in the past.