I've been thinking about this for some time now. I haven't really conceptualized much but basically I was thinking of these characteristics:
A. A 2D game B. A non-profitable game
Alas many problems arise. For one, the genre of the game; a mix of genres or one solid genre? I'd have to say it would fall under several of these categories: platformer, role-playing, fighting, shooter, and action-adventure. Another problem is that it's hard to make a game based on a book when in a book there isn't all that much action that you could use in a game. Usually the developers twist and turn it. Take your typical game based on a movie. They have all these extra stuff in order to make it interesting. Now, on to the third problem, we'd need sound, music, sprites, and a game engine/creator. There doesn't necessarily have to be programming involved(take for example Game Maker, Multimedia Fusion 2). I personally am not good at all these subjects-- But with practice, I might. I have a knack for art and music, but I'm not very good. I plan taking art classes soon. You also have to make the actors and props out of pixels, not drawings on paper (though you can make concept art with paper and pencil). The events (or programming) would not require a great deal talent though. As you can see this project would take a lot of work.
Whatever book its based on, it would be one that has many adventures and battles. Because journeys to destinations could easily be filled with game attributes. And the battles even more. But alas the characters in Redwall show a lot of emotion and talk a lot. The game would be more of an experience of using your favorite character, fighting vermin, and living in the Redwall world; rather than conversations, and lots of emotion. Anyway, that's all I have to say. It's just an idea-- and might not even get it off the shelf. Just think about it and tell me what you think.