"We were just wondering if it's good to leave a few things to chance?"
"We want to give your child the best possible start. Believe me, we have enough imperfection built in already. Your child doesn't need any more additional burdens. Keep in mind, this child is still you. Simply the best of you. You could conceive naturally a thousand times and never get such a result."
-- Gattaca
However -
The story of the film tells us time and time again that Vincent -isn't- able to compete and measure up to the standards needed for space travel. He fails his cardio tests, he can't see well enough to cross the street. But his vanity and pride causes him to cheat the system to make it seem like he passes all the tests. He has the heart of a fighter figuratively but not literally and I always imagined after the end of the movie that his actual faults would come to light and it would cost someone their lives in space.
What if he lost a contact lens in space? They don't have more. What if there was an emergency and they needed someone with an expected amount of endurance to help save everyone? Gattaca for me always told a different, darker story. I think the story they wanted was a caste story - if he was just as able and strong but beat out the genetically superior people on their terms then that would have been the story they were trying to tell. In the end, they told the story of a clever cheater who put his own wants above those in a delicate mission and it's left to a guess if that cost lives or no.
During a talk with another person on this, he supposed that this is why Jerome incinerates himself at the end. He needed a lowly sort as such as Vincent to fulfill his own dream, and in the end just could not reconcile how he may have just destroyed and polluted the whole of his pure society for his own selfish reasons.
To have Vincent be just as genetically able and strong would defeat the whole point. Not all men are born equal, life is unfair but we should all aspire to reach for our dreams despite our limitations. If we take things to their materialistic dead-end we get a single man optimally selected for a single task from his birth unto his death like a machine with no room for error, or chance, or humanity.