The OP is writing about how to "get into the heads" of opponents--which for many, under the pressure of competing is not too difficult. I've seen at 4.0 sectionals some guys totally come unhinged when called for a foot-fault by the roving referee. One guy was a lawyer, who started arguing with the ref that it was "Only a technical violation", as only a lawyer could and persisted in foot-faulting and arguing with the ref, who called him on each additional foot fault until he lost the match, much to the dismay of his team-mate--hilarious!
It's very easy to correct for a foot-fault if you have a sound serve--you just move back a few inches and the problem is solved without coming unglued mentally. Sometimes if my serve is going long, I'll step back a few inches to keep it in for a quick fix.
At the same tournament that "Clarence Darrow" was in, I saw another instance of foot faulting being called where the perp did not become temporarily insane. It was in dubs and the roving ref called an f-f on a player who was NOT over the service line. The player was mystified why and the ref said to him you can ask me why and then I can tell you. The player asked, he was stepping over the imaginary line between the deuce/ad sides at the hash mark--which was unusual for doubles. This player handled it much differently then the lawyer in the previous example, fixed it and went merrily on his way.
"...the human emotional system was not designed to endure the mental rigors of a tennis match." Dr. Allen Fox