I was bugged by the lightsaber part of your theory since Luke had constructed his own after he lost the one Ben gave him in The Empire Strikes Back. But now it makes even more sense. Luke’s lightsaber in Return of the Jedi is green while the one he lost in Cloud City and the one “calling” for Ray is blue. Thus the one Ray found has to be the one of Obi Wan. It would be rather disappointing if they mixed that up…
Btw why does the new big, badass boss look like Voldemort? Are they going to find secret plans in another new Droid about where his Horcruxes are hidden in the next episode?