If I was Disney, I would have JEJ recording dialogue from now until the day he dies. I dunno, just have him read dialgoue from every script fir every film ever written, then just go through recipe books etc. Cut and paste words until you get the Vader dialogue you want. Own his voice in perpetuity. Yes.
I think Chewie actually looks younger in the more recent films. Maybe he has just discovered Pantene Po-V with conditioner or something.