I hate to say this, but Mark Hamill’s voice in this audiobook sounds quite different from how he sounded in the Sequel Trilogy. His voice is a lot more gravely. What I think you should do, Jar Jar, is use AI software to cleanly isolate Hamill’s dialogue from Episodes VIII and IX, as well as the deleted scenes, and use that to sample for Luke’s new dialogue.
I agree, Mark uses a much deeper voice in the films. Like I said before, I’m not willing to do all of that work myself, but if somebody wants to give me the audio files I can synthesize them.