Mustaches vs tentacles on Hawaii! So, yes, just take the basic idea of Magnum, P.I.: it's the 1980s, the group of protagonists are security experts, bodyguards, private investigators (some of them Vietnam vets) etc., who work for a mysterious rich patron (who only communicates through recordings or the trusted estate manager). Initially, their job includes perimeter checks at the mansion, low-key investigative work... but eventually the weirdness ramps up as the mysterious patron's missions become more mysterious and plunge the team into the depths of cosmic madness.
Yeah... just a random game idea for this lazy Saturday afternoon.
I kinda dig the [something + Cthulhu] formula. You know, like Scooby Doo + Call of Cthulhu.