For me, the issue is less the lightsaber and more the fact that Luke expressed his wish to become a Jedi like his father, and the only mentor (supposedly) who could make that happen is dead by the end of the movie. That, along with the survival of Vader and the Emperor, are the two biggest reasons why the movie needed a sequel, in my opinion.
The emperor is inconsequential in the original movie. And with the novelization taken into account, he’s only the latest in a line of impotent figureheads, anyway.