Let's aim, not just to regrow broken spinal cords, but to restore anyone to physical youth who wants it. Let's aim, not just to optimize the learning ability of the brains we are born with, but to boost that ability to unnatural levels through technological means.
Well, first of all, the term "optimize" always contains an unstated "optimize -- in the service of which ends for what for whom": it isn't a neutral term, but a term occluding all sorts of moral, aesthetic, political contestations around what is meant by intelligence, what and who counts as intelligent, what intelligence is good for. The tendency of you transhumanist types to go off willy-nilly speaking of "enhancement" this and "optimiziation" that as though all these contestations either don't exist or aren't important typically makes transhumanist discourses on non-normative medical and prosthetic and cultural interventions stealthily eugenic (no doubt unintentionally in many cases) in addition to all the other idiotic and wrongheaded things they also tend to be.
But to speak more directly to your point here, I must say that I do not agree with you about the force of the "aim" you are mobilizing in your statement here. I think scientific and medical research tends to be driven by the proximately possible, I think its terms are suffused with laboratory conditions, funding exigencies, ongoing publications.
I don't doubt that many scientists also enjoy indulging in blue-skying about how cool it might be if we could one day regrow limbs or live for centuries or employ nanoscale techniques to change dirt to feasts and mansions for peanuts...
And I don't doubt that this sort of daydreaming fuels the imagination that drives some creative science in the lab or in the published paper, just as for others creative science is driven by the contemplation of God or James Joyce or a night of drunkenness or a night with a lover or a long suppressed traumatic event from childhood.
Even if we should grant and celebrate the often unscientific wellsprings to which the imaginative or motivational dimensions of critical, scientific, problem-solving rationality are sometimes indispensably indebted we need not and indeed should not confuse them for critical, scientific, problem-solving rationality themselves.
As anything but diffusely inspirational expressions of "wouldn't it be cool if," utterances like "let's aim for soopergenius IQs in sooper bodies that live for centuries in the Oort Cloud" have no legible connection to what is practically meant by "aiming" for anything at all where the rubber hits the road in laboratory practice, in the writing of the paper or the grant request or the regulatory study. Confusing such matters isn't a sign of superiority but of error or ignorance (some of it willful), and it is the furthest imaginable thing from helpful.