(Subsidising equality via the state doesn't sound 'libertarian', and Headstart has been ineffective, but I'll leave that aside)

I think your solution cannot happen because those with money and tech, and who don't have a cultural squeamishness with the idea, will get the genetic engineering first. The ultrarich. Probably the Chinese, maybe others. Then it will be a case of making the rest of the world amenable to these enhanced people. Elites don't want chaos and nor do they want anyone to threaten their dominance. So a functioning, intelligent, but malleable mass will be controlled by an elite who have the tech. Just as today the average joe doesn't have access to nuclear weapons.