The Wormhole wrote:
Eccleston not returning as the Ninth Doctor is the most obvious missing element
Especially considering the Moment is trying to show the War Doctor what he'll become if he goes ahead and obliterates Gallifrey. You'd think the first incarnation to deal with the guilt and torment over how the Time War ended would be a pivotal one for the Moment's presentation. Hell, imagine the scene where the War Doctor asks about how many children were on Gallifrey at the end were Eccleston in it. He still hasn't brought himself to finding out, Tennant knows the number, and Smith has forgotten it.
Yeah, I know, it's pointless to speculate on what could have been, especially considering there likely wasn't very much of a chance of Eccleston returning for this. But one can still imagine anyway.
The million dollar question is this: Had Eccleston said YES, would Moffat had written it with the War Doctor STILL, and had him meet all THREE of his future regenerations...
...or would Eccleston taken the place OF the War Doctor, meaning no John Hurt but rather him in that place with very minor script changes?
It could work either way. He'd fit into the whole :TRhe one that regrets" and "The one that forgets" part as "The one that hates himself" or some such. But he also could have worked in the Hurt role.
Guess we'll never know.