You'd need to have two modes - a "regular" mode for a standard 3-ball pinball game and an "advanced" mode for an RPG-style game. Essentially two games.
Otherwise you'd be severely limiting the audience by eliminating the casual walk-up player.
I have a design for an RPG-style game that could really work but it also minimizes the turn-based drawbacks of the genre. Even as an "RPG-lite" it would only be appealing to crazy pinball nerds.