In another thread someone quoted a recent WT source that said the use of the cross in illustrations was abandoned in 1936. I came across this booklet "What is Truth?", written by Rutherford in 1932. It shows Christ on a stake on page 56:
But, it's just an illustration. This could not be the introduction of the idea. (As I recall, this was about the time the WT was redesigned with the result the cover no longer had a cross on it.) There has to have been an article somewhere that first presented the view that Christ died on a stake instead of a cross. In a Watchtower of that era? My guess is that perhaps it was in a Golden Age magazine before this 1932 booklet was printed? Does anyone know?