If you check off on your license that you are willing to be an organ donor, then the doctor who is harvesting your organs does not need to wait until you’re halachically dead in order to remove them.
In such a case according to halacha the good doctor is committing murder. By allowing the doctor to harvest your organs while you are still alive, you are an accomplice to murder.
Hence commiting to donate your organs is being an accomplice to your own murder. No feel good ethical rationale can justify this.