Maybe that is why each jedi is supposed to make their own lightsaber. That way, they can customize it to include various safety features only they know about, there by making it hard to operate by others (at least by others without the advantage of touching the thing directly).

Like having a mechanism that requires them to put pressure on a specific place with their index finger when turning it on. And another place with the pinky finger when turning it on (since turning on the opponent's lightsaber when it is stored on their belt next to their junk seems like something a Sith would totally do).

The answer too this is simple: Force shields. Jedi/Sith worth any dignity of using the word to describe themselves can make a force shield to defend their general area from enemy force users during the fight. Likewise it takes time to concentrate for some force users to break through shields unless the fight is one sided as hell. Go ahead and try to disable that lightsaber as i protect it and jab you through the chest with it because you're weaker in the force and took the chance in hoping i'm overconfident enough not to make a shield. If you're able to get through the shield your better off just rag dolling the person with a force push or pull of some sort. Obi-wan couldn't defend against Dooku for example because while Kenobi is a waving motion of near impenetrable defensive brilliance and one of the best soresu masters EVER he still could only muster a passable force wall. Dooku on the other hand…Dooku was a boss with the force.