I wanna know which RPG system or variants would work best. D20 as is wouldn't work. A DM should override rules for the sake of drama but some of the OotS characters go into total rule abandonment. For example, Belkar's small daggers can cut hydra necks. Durkon, by amazing fortune, happened to have two Sanctuaries prepared in the Pit of Outdated Monsters. Not one of Tsukiko's attack spells hit Mr Scruffy.

There would have to a framework, whether explicit or implicit, about what cliches override the dice and rules.