My theory about why the light saber has a fixed length blade, is that the blade is created by squeezing a plasma ball with a forcefield in the handle. If that’s true, then it should be possible to just fire an unsqueezed plasma ball out of the handle, creating a projectile weapon. Its a bummer they never did that.
The Jedi kid in Star Wars Rebels has built a blaster into the hilt of his lightsaber.