Even you admit that he was definantly an indivudal with his own consciousness. So from LEGAL point of view doesn't this individual with a consciousness have a right to live?
This is where your argument falls apart, the only argument you can make using Legality
is conjecture on your part. You don't know what is legal or not in Janeway's situation or time for that matter.
You assume it is a problem, some of us assume that it is not a problem. The evidence on our side is that Janeway got home and a couple of years later we see her promoted in rank. Where is your evidence?
Ethics is one argument but legality is a completely different argument and you have no base in canon to make that argument. Canon it would seem supports Janeway's decision.
Edited to add
Since I have already stated that in the US organ donation is illegal without the consent of the donor or a qualified representative of the donor. I thought it might be nice to know what is legal in Great Britain for MacLeod's basis for Legality
Section 43 of the HT Act gives limited exception to the requirement for consent so that the fewest number of steps may be taken after death, using the least invasive techniques, to preserve organs while consent is sought for donation; the suggested techniques are intravascular or intraperitoneal cooling. ‘Appropriate’ consent must be obtained for removal, storage and use of organs or tissues for transplantation. Consent may have been given by the donor while alive, and voluntary organ donor registration by a competent minor or adult is deemed to constitute informed consent. If the deceased had nominated a representative while he or she was a competent adult, that person can consent to donation. Otherwise, a qualifying relative may be approached to give consent. At the top of the eight-step hierarchy of qualifying relatives is spouse or partner, and at the bottom is a friend of long-standing. A child cannot have a spouse or partner, so parent is his highest qualifying relative. The HT Act accepts that there may be reasons in certain cases and circumstances to vary the hierarchy, and the urgency of finding someone to consent to donation could be such a circumstance. Consent conditional on who will receive a cadaveric donation is not accepted. There is no guidance to organ procurement in cases where consent is unobtainable, and it is important to emphasise that procurement without consent has been made unlawful.