There have already been multiple suggestions on how to fix here in this thread. It's not really an issue since it's so easily fixed.
Except, it isn't so easily fixed.
I went ahead and double checked the concentration mechanics: "The DM might also decide that certain environmental phenomena, such as a wave crashing over you while you're on a storm-tossed ship, require you to succeed on a DC 10 Constitution saving throw to maintain concentration on a spell. " is the only version that doesn't require an attack roll first. Even something like Stinking Cloud which can cause you to spend an entire round retching do not trigger concentration checks.
So binding someone in such a way that they always need a concentration check would be incredibly difficult. And I am not sure how one would go about it per RAW, without creating a damage over time effect.
And the exhaustion sounds good, except to prevent someone from sleeping, you'd have to be awake yourself, and a single level of exhaustion goes away with a single nights sleep, so you'd need to have two nights without sleep, then get a night of sleep, then they have to go everyother day without sleep.
That is a highly complicated system, and it only gives you a
chance to stop them from using their psionic powers.
Meanwhile, tie a wizard up and gag them, and they absolutely cannot use their powers. Heck, use a ball gag with a lock and you don't even need to tie them up.
That is a major difference in power.