In GT, I always turned the music off, so I don't care about playing my own selections with it.

What I would miss is the ability to make major changes to the cars performance and appearance [such as the racing bodies in the original game of the series], and being able to have the full choice of new cars any time. And it would be cool to have the old used car lot thing, too; it added something to one's involvement with the game to buy an old one and modify it into something radically faster. Sorta like hotrodding in real life.