This reminds me of one of my favorite threads on the old Internet Infidels web site, in their Philosophy forum. The question was, "Do dogs bark?" There was an enormous amount of discussion on it!

Does "when pigs fly" imply that some day pigs will be able to fly? No; people can understand impossibility when it is used rhetorically in every day speech.

For example I might say, "all the honest politicians are doing a great job", which conveys my actual meaning, "all politicians are dishonest".

That stops working when its not obviously rhetorical.

Someone else in the thread mentioned: 'All my kids are in high school'. If you said this to a stranger with no other context, they will 100% think that you have kids. There is no possibility that you meant, 'I am asserting that in the set of my children, each element satisfies the property of being in high school'

I don't understand what point those examples are supposed to convey.

"All of my unicorns can fly -> some of my unicorns can fly -> at least one of my unicorns can fly" still seems to be a valid inference that may get lost in conventional translation into first order logic. And a proposed "allsome" quantifier still seems like a valid remedy for that.