I wouldn’t focus solely on the religious angle. I would bring in the Nuremburg angle prohibiting forced cooperation in medical experimentation, citing the adverse vaccine reactions that have been widely reported, along with the extremely low rate of risk that Covid carries for people under 50.
The legal question will be if the federal executive branch has the legal authority to mandate federal government employees be vaccinated if they don’t want to. Remember, Biden basically said, “jab or job,” as they removed the ability to request an accommodation. I doubt SCOTUS will rule on the right of the feds to do this, but they’ll likely say they can’t disallow a religious or health accommodation.