Sometimes all these dreams are useful

I had a dream last night that has led me to think of a super-cool duo for mystery novels. (In the tradition of Holmes/Watson, Rex Stout/Archie, Poirot/Hastings -- but different enough that it's not just all of those smushed together and gender-swapped.) My problem: I'm not very good at thinking up mysteries. Maybe my bar is too high for making them myself; I want them to be tough to solve, like Agatha Christie mysteries. But most mystery novels aren't like that. Another problem: I would want them to take place in the modern day, but be more like Sherlock Holmes than modern mysteries. Realism in character, yes; realism in "this is how private investigators actually work", no. Maybe I should try some kind of steampunk thing.