That's the rub, really. Who decides what's an improvement?
Even "improvements" done with the best of intentions will never be free of unintended consequences.
Who gets improved? Will have and have not divide ultimately result in Morlocks and Eloi and such?
And, of course, all is well until the EM pulse, computer virus, resulting insanity, etc.
Most humans don't know how to appreciate what they already have. Giving them the ability to choose their own "improvements" is like giving a three year old the ability choose dinner. How can candy for every meal be a bad thing?
I'm suddenly reminded of a quote...
-- Susan Ertz, Anger in the Sky