What people, technology, methods, etc... would have made sense to make a return appearance in Trek? I'm not meaning some character or creature that was underused or a "one shot wonder," that we would like to have seen again. No, I mean that something that would have made sense to be seen or used again. Something that "should have" made a return appearance. Something that made us viewers think "why didn't they just..."
Example: In TNG's Allegiance, Picard is kidnapped by aliens to be studied. When they return him to the bridge of the Enterprise, Picard turns the table on them. Without verbal communication, Picard signals his bridge crew to implement a procedure that traps the aliens in a forcefield (similar idea to the Bridge defense system in TAS Beyond the Farthest Star).
If the Enterprise has such a defense system that can quickly secure the Bridge from intruders, why was it never used again?
Example: In TNG's Allegiance, Picard is kidnapped by aliens to be studied. When they return him to the bridge of the Enterprise, Picard turns the table on them. Without verbal communication, Picard signals his bridge crew to implement a procedure that traps the aliens in a forcefield (similar idea to the Bridge defense system in TAS Beyond the Farthest Star).
If the Enterprise has such a defense system that can quickly secure the Bridge from intruders, why was it never used again?