On current showing, anything designed by humans would be doing well if it resembled the later works of Boris Artzybasheff. Most of our best suggestions would be pedestrian, such as re-routing our recurrent laryngeal nerve, separating our fluid and gas transmission routes, and similar tinkering.
A serious attempt at redesign would involve a lot of radical changes, including mental, social and reproductive as well as physiological. Too much even for one of my screeds. I have long been disgusted to nausea by the sheer barrenness of imagination and biological insight of the designers of aliens in star wars etc.
