Wait, what exactly is wrong about the last one? It sounds odd, but not so incorrect, to me.
Edit: this is in reference to "brick the barn". Grammatical if nonsensical. "Brick ancient barn" is of course weird and wrong unless you really want to emphasize that this is a brick ancient barn and not a wooden ancient barn like all the other ancient barns. The normal adjective order can be deviated from for emphasis. My point was that that didn't work when "the" was one of the "adjectives".
(I've been trying to fall asleep for hours so I make mistakes left and right -- I apologize for not being clear about the word list I referred to.)
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"Grain silo" and "fish pond" are exactly-precisely compound nouns. It's just that English refuses to accept that it's a Germanic language and instead puts on airs. Honest languages would of course never dream of inserting pretentious spaces between the constituent parts.
I actually thought of "stone chimney" as a compound noun instead of adjective + noun when I wrote it, precisely because I wanted to mock that and really hammer home the point. Unfortunately, the two look the same in English (but not in Danish) -- and I was tired -- so I didn't catch it and replace it with a better example.
Eeeh, not exactly in English. English does make some distinction between fully compounded words and noun phrases, especially in rules of production. In a newer phrase like "wind farm", you can swap in more or less any noun you like, even if it doesn't make a lot of sense: "mud farm", "rock farm", "hair farm"... there's some rule like "substance + farm = a farm that produces that substance". With a word like "bedroom", you can get "bathroom", but not so much "deskroom"; there's no general rule like "furniture + room = room where that furniture is found". The space (in cases where it's pronounced) is kinda your hint there.
Anyway... I still don't believe in grammar, but y'all have mounted a spirited defense of the traditional analysis. I'm sorry I tried to say everything's an adjective :)
Most people would be comfortable saying "ancient grey brick barn".