I hate to be pedantic here, but I think you mean "shill" instead of "shrill". Technically what you did there is called a malapropism, where two similar sounding words are misused because the alternative wording could make sense as well. I always thought the saying was "for all intensive purposes", but the actual saying is "for all intents and purposes".
However I like the use of shrill in this context, as even though it is technically incorrect it made me think of a little bird being paid to shriek nonsense.
