The issue with puzzles that vary based on difficulty is because one would have to make several versions of that puzzle and make sure its solvable as well so they cant just generate and place it in, unless they somehow cracked a peice of code to do the testing it is really hard to do.

That's basically how System Shock did it. Stuff like the door codes stay the same cuz they're in voiced audio logs (save for one that's randomized each time you play) but the wiring puzzles get considerably more complex on higher difficulties.