The biggest feature for me would be to continue playing a saved game from the previous release. Ever since short people calling me "Dad" started appearing in my house, I just haven't been able to get through the game much before the next year's shiny model appears.
I realize that the new version may store stats or come with new categories of data that the old version won't have, and things might need to be fudged when converting the save game, but that's better than never getting anywhere in the darn game.
While we're at it, in general, features that help one to play through the game faster would be useful.
Thanks, and especially thanks for making the game available through Steam.