As I said in the C&P up there, it's pointless. I'll go into more detail now for the hard of thinking.
If you can add the upgrades and race, why would anyone else choose NOT to add the upgrades since they would then be slower and have no chance of winning?
Eventually, someone would figure out "oh, this upgrade is pointless for this track, but this one really helps lap times" and everyone would start copying them. Eventually you would actually NEED that same list of upgrades to compete on the track. So every car in the race would either use them or be out of the running. And if every car is the same, guess what? Yup, we're back where we started.