You may want to start your review with the 2001 U.S. Supreme Court case of Egelhoff v. Egelhoff (121 S. Ct. 1322) and the 2009 U.S. Supreme Court case of Kennedy v. Plan Administrator for DuPont Savings and Investment Plan (129 S. Ct. 865) generally holding that death benefits under an ERISA plan are payable only in accordance with its terms.
I add that I have seen disclaimers used after death to allow a different person to receive aN ERISA plan death benefit, but likely would not be useful in this instance. Under a disclaimer, the designated beneficiary disclaims his or her right to receive the death benefit. The effect of a disclaimer is that the beneficiary will be treated as dying before the participant, and the resulting beneficiary determined in accordance with the applicable plan terms. A disclaimer cannot designate a beneficiary for the death benefit or otherwise direct its payment.