Instead of remove CAREER mode how about made it more shiny CAREER mode with multiplayer option.
So you can start a brand new career mode in multiplayer.
I would say players would like to play career mode with friend(s). Like there is 4 friends who would like to play together and they could play career mode together instead of just a single race or Co-op championship i personality would vote for Multiplayer Career Mode. Where you can fight with friends for team contracts and get good team for you. Just a TiP