I observed that 'idiot' is sometimes used as a modifier, which, as grammar.ccc says, 'are like teenagers: they fall in love with whatever they're next to. Make sure they're next to something they ought to modify!'
Some instances of real English usage I found, among others, are the following:
What kind of idiot teenager agrees to baby-sit on a millennial New Year's Eve, anyhow?
They tried a plastic slide, but some idiot teenager broke it. Wood? It splinters as it ages.
Other than those there are a lot of other example, especially in reference to children, boys and girls.
So, I would like to know whether the English language has some limit in using 'idiot' as a modifier outside those cases.
I ask because I want to say that a friend of mine has an 'idiot smile', but after searching a bit I didn't find a lot of occurence of that expression and it seems that 'idiotic smile' is preferred.