The two outer rings by themselves can, with their current alphabets (that is, A through Z in order on both) be used for any Caesar cipher…that is, the kind of shift cipher you’re talking about.
But keep in mind that with one or both outer ring alphabets in non-alphabetical orders they can be used for non-Caesar monoalphabetic ciphers. And because the six inner rings can also be arbitrary alphabets, this wheel format can, and in the game does, implement polyalphabetic substitution ciphers.
But yeah, the logic for doing the related puzzles in a text-only interface is already in the game code. I released a TADS3 module that implements a bunch of cipher algorithms last year and in slightly modified form that’s what’s used in the game.