Wow!! Like Sibhusky and JMD have said, that's a tough order to fill.
If you are set on 1 pair of skis for racing AND powder AND bumps, then you will have to compromise on all sides. There may be a ski that can "do" everything you are asking for, but not a ski that will do everything well.
As has been suggested already, you could look for a pair of cheap used GS skis for racing and supplement with a pair of fat boards for your western trips. A pair of used GS skis will perform much better in a GS course than any 90+ ski ever can. However, if your involvement in racing is really just for recreation, then you probably don't need a dedicated racing ski.
If you can only go with a 1 ski quiver for everything, then my suggestion would be something in the 85 - 95 mm range under foot. It will do OK in a GS course and handle bumps and powder OK. Any fatter and you will be sacrificing in the course; any narrower and you will be sacrificing in the powder.