I'm over a year late, and I doubt this thread is being watched anymore but this is a good idea. There are some songs that I listen to that I just can't quite hear what they're saying. You'd have to get reliable lyrics from somewhere, as I don't think there is any way to get them from the song itself. Unless of course you listen to it over and over until you figure it out and then type them in your self. Is that what you meant? The user puts in the lyrics for themselves? This, I think, is feasable.
I think it would have to come with a small DX Player, you know, just for the purpose of getting lyrics.
You can save the user settings to a text file which can later be recalled at any time. I guess it wouldn't be a bad idea to have the ability to save the lyrics to each song seprarately in individual text files. Then save the user settings, such as speed, to a configuration file (a fancy text file).