It wouldn't be so much of a retcon like you are suggesting. When filming the Palpatine's arrest scene, Kit Fisto is 'killed' and his body is on the floor. Mace steps over it mid fight. But later in the fight, they go back to where it was and the body is gone. Now this was obviously a mistake in filming, but wouldn't it be far more interesting to have it so Kit Fisto survived his wound (which did seem perfectly survivable) and was forced to make his escape as he knew he wouldn't be any help (I agree that Kit Fisto was outmatched by Sidious). Instinct tells him to take his own personal craft and when he sees the temple burning, he knows he has to go into hiding. I think that would be a cool and handy way to get rid of an error in Revenge, and it could fit perfectly well into the existing Canon timeline.