Create that default race, start your game. Then, in SM mode, create a new system (see change logs on how to tweak Systems). Make a suitable planet (nitrogen oxygen), then create a race (same window).
Save, restart and you can access your new race and play with it.
In Systems view, delete Sol, then change your race in tactical view to player race (some errors), then in race menu you can finally delate player race. And you're set