Board Thread:General Discussion/@comment-79.24.170.237-20160510203254/@comment-27384850-20190110011746

It would be impossible to bring Yuuki back due to the functions of the Medicuboid and the nature of her death.

The Medicuboid is stated to be basically a high-powered NerveGear; it connects to the user's brain all the same, it just has a stronger output and more pulse-generated components. Because it's basically an industrial-strength NerveGear, copying one's brain a la what Kayaba did would burn it out and kill them.

Yuuki's death was a result of her condition--her AIDS. What this means is that it was not the result of her brain being scanned by the Medicuboid, as that would have caused her death had it been the case. Because of this, her brain having been scanned like Kayaba's could not have happened.