I think it'd be really cool if you could make your myplayer (or a player locked player in a myleague) go to different leagues. I understand that a lot of it has to do with licensing, but it could be made up leagues or leagues that we as a community create.
In fifas player career mode you literally pick any league in the world and what team you want to start at, then you get offers from other leagues and teams at the end of the season. So in basketball it'd be like starting in high school or college, then maybe going to a lower level league somewhere in Europe and bounce around Europe or Asia, until you make it to the league. Or you could stay in Europe your whole career!
I think it'd be really fun to play all over the world in different countries and leagues, especially if 2k could get licensing for some leagues. It doesn't have to have a story like my career, but just the option of playing in whatever country you want and not just in the NBA, seems really cool to me! Hopefully some people agree with me on this!