Using an AI trained by Jar Jar’s lines to replace his dialogue seems a lot more respectable to Ahmed Best’s performance compared to throwing out his voice entirely. I don’t see much of an ethical issue here beyond just what comes standard with taking someone else’s work and recutting it to suit your taste. This also seems great for making edits that would stand up fine alongside canon media or others’ edits, since it can indeed be jarring going from a redubbed Jar Jar to the official voice.
It’s not really a matter of “respecting the original performance” for me. I’d argue that any form of fanediting could be considered disrespectful to the original creators, because it implies that there’s something wrong with their work. My concerns are mostly based around getting the best possible performance: an AI is inherently less capable of expressing emotion than a human being. No matter how good these AI programs get, they will never sound “human” to me.
Also, as long as the new voice is reasonably similar to the original, I don’t think canon compatibility is a huge issue. Characters change actors in official media all the time. I personally think canon compatibility is an overrated concept in the first place, but that’s another issue.