currently there is no Genetic engineering that involves sex chromosomes.
when scientists work with genetic engineering believe it or not the motive isn't to make freaks or super humans. It is actually to help people with serious diseases.
Take SCID for example.. Severe combined immune deficiency ( think bubble boy) who died when taken out of his bubble... This disease was successfully treated in a few patients using Gene Therapy--
requirements
The gene must be identified and cloned.This has been done for the ADA gene.
It must be inserted in cells that can take up long-term residence in the patient. So far, this means removing the patient's own cells, treating them in tissue culture, and then returning them to the patient.
It must be inserted in the DNA so that it will be expressed adequately; that is, transcribed and translated with sufficient efficiency that worthwhile amounts of the enzyme are produced.
Scientists are trying to use gene therapy to wipe out genetic diseases which people normally don't survive, SCID being one, lysosomal storage disease, glycogen storage diseases and even some cancers with genetic predisposition. People in politics are evil, I fully believe that... some scholars who pass fatwas are ignorant or acting from what they believe is right-- even though it might not be-- I am not saying people in science aren't evil-- but believe me more of a concern is saving lives than altering human makeup.
I mean think of it this way. Not everything is so very black and white, so you use your Islam and your knowledge to do good not bad and decide for your person since you'll be raised on your intentions not communal efforts
Is plastic surgery Haram? could be if you are completely altering your appearance, is it Haram when you have a mucor (fungal infections) that eats away half the face and a person is in need of debridement and serious plastic surgery to restore breathing and function to newly denuded areas?.....
Is choosing the sex of your child Haram? I personally think it is, but is wanting to help save your child from a serious fatal disease Haram? I'll leave that answer to your discretion
fi aman illah