Wasn't aware there was a thread, sorry about that. Should this thread be pruned, or keep it?
Beyond that, I also think if he's the one who ended the Time War would be anticlimactic. And, it wouldn't be a secret, now would it? The secret is aimed at the viewers too, and all fans that watch the show know this.
But perhaps, if he has to be the 8.5 Doctor, he's the one that started the War?
IIRC, RTD's stance was that the Time Lords recruiting the Fourth Doctor in Genesis of the Daleks was actually the start of the war.