Someone who never played on a Walker Cup team, never won the US Amateur, was never USGA President, but was Walker Cup captain was...........Lou Oehmig.
He was a six-time finalist, and three time winner (72,76,85) of Senior US amateur.
Mr. Oehmig was captain for victorious 1977 team at Shinnecock. He also won the Bobby Jones award, the highest USGA award in 1994.
Having mentioned Lou Oehmig, I do not think something like that would happen again.
And prior to that, Tufts and Winters were captains who never played on Walker Cup, and were not USGA champions. They were past USGA Presidents who were later WC captains.