I don't think introducing a third actor or a digital recreation is a good idea.
Ewan nailed it, why over complicate things further?
I think because having Ewan play Older Obi after the original trilogy would be just as bad and inconsistent. Ewan did nail it...but he nailed it being the younger version. Having him appear after Alec's time would be equally as bad IMO. I say if it can't be done right, then leave it alone and don't have Obi appear at all in the new films.
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