FWIW, I don’t regard that cameo as being the youngling character himself, but an unspecified Jedi from sometime within the last 1000 generations we hadn’t already met in the movies.

And in an edit that still has Hayden Christensen as Anakin’s ghost, I don’t think it makes sense to replace Ewan McGregor’s actual voice with an AI of Alec Guiness. Whether there’s a worthwhile line to toss in is another question, but it might be more of a cool idea that could be done rather than satisfying a need.