Tommy and Tuppence are supposed to fit the OP’s bill: “it’s quite impossible to lead him astray through his imagination. He hasn’t got any – so he’s difficult to deceive. He worries things out slowly, and once he’s got hold of anything he doesn’t let go. The little lady’s quite different. More intuition and less common sense. They make a pretty pair working together. Pace and stamina.”
And, to an extent, it’s true. Upon setting up shop in their own detective agency, she’s brilliant and unconventional – “solving” their first case in front of her slack-jawed partner (by dint of staging the fake crime to begin with); faking psychic powers on a genuine case that follows (“Oh, that was just cheating,” said Tuppence happily. “I opened her letter…”); cracking an otherwise unbreakable alibi by falling asleep so her subconscious can come up with “rather a funny idea. Not at all like anything I have ever read in detective stories” while he’s been trying to do it by the book, showing photographs to all the right people and greasing palms; that sort of thing.
For bonus points, they’re so genre-savvy that Tuppence initiates one case by saying “I am going to be the star, and you will be the humble assistant” – which prompts Tommy to note “that it’s always an innocent remark by the simple Denny that puts McCarty on the right track” – and, of course, after they’re well stymied for a bit, he eventually says something innocuous that sparks her bewildered stare and a congratulatory “It’s just as you said. One simple remark!”
Needless to say, he also handles the physical bravery in between keeping up smooth relations with the authorities; it’s not a perfect parallel by any stretch (as he’s too good a sleuth and she’s too good with people), but you could do a lot worse.