I think most pitchers have experimented with this at one time or another. Mostly out of a sense of curiosity, and to see how well they can pull it off.
It's sort of one of those anomalies to safely test at a scrimmage/ practice, or low risk situation, when adding a little spice to a game and witnessing the reaction to it from both sides could be beneficial...
Still....at the end of the day, and regardless of how the ruling is spelled out within any given sanction, you're ultimately at the mercy of whatever the plate umpire perceives to be the right call. If you are the coach that called the pitch, even though you may technically be on solid ground within the rules, it doesn't necessarily mean that it will be called that way by EVERY plate umpire. You're going to face some disparity in how it's perceived and called, and it's a risk that you assume on your part.
I would imagine that most umpires would rather not have to issue a ruling on this on such short notice, so I would say that any coaches odds in getting this called as legal would be <50% of the time.