FERS would enable him to designate a primary beneficiary should he die, but it is in the name of the employee and accrues money each two-week pay period. I don't see a way around that. And given his pay scale, he would top $5k in a matter of a few months.
Maybe our resident magat accountant can fill us in.
I don't believe OPM will give your pay to someone you designate due to tax liability issues. Once in your account, you could do an automatic transfer to someone else. In my experience, every once in a while, a neo-luddite new government employee will try to get around their system by having a check mailed to them. I was in the old system that grandfathered in which Congress had, and I kept not signing up for direct deposit, and made it several years more getting a paycheck mailed, but eventually some officious bureaucrat forced me to give them a direct deposit routing number or threatened to hold my pay until I did. I mostly did it just to see what would happen, since I detest bankers and credit card companies, and my general orneriness. It only worked because I was already in the system, a new employee requires an account.
I do see one avenue though. If he donated all of his net pay to the Combined Federal Campaign charity and designated a church as the recipient, he could avoid having a bank account, but because of the charity rules he would lose control of the money. Scam churches wouldn't qualify as they are thoroughly vetted to avoid scandal. Would make it tough to pay the mortgage for him unless someone is paying it for him, like Clarence Thomas' mother enjoys, or his RV loan. Off the books money from a donor to live on... that would be a cool gig, if you could get it. My bigger question is why would someone go to all this trouble, to avoid taxes?.. since his paycheck would be subject to withholding anyway.
If he doesn't come clean, it is only a matter of time before Anonymous or someone will hack him and get to the bottom of it.