Stick to those guns! I wouldn't mind the Valeyard, but I'm not sure why the Dr would need a memory block and/or have memories of a future Doctor unless it's prior memories of the Valeyard from the Matrix or something.
Trial of the TimeLord. He knows the Valeyard is him, and he knows it WILL happen. It's an inevitability. This does kinda not mix with my previous theory of the Dreamlord being the genesis of the Valeyard, but still, I'll takes what I gets. However...
What we know:
1) He is a secret only The Doctor knows supposedly. This hints to the Time War, since there were other people who knew about The Valeyard (including TGI, who said as such in this episode) and the folks involved in the Time War are presumably all dead. So that rules out The Valeyard.
2) Clara did not see that Doctor regeneration, but presumably she had access to virtually his entire timeline. If that regeneration was during the Time Locked period of time, it would explain why Clara never saw him.
3) John Hurt says he did what he did for "peace and sanity". The Valeyard was just an asshole. However, The Doctor would have justified ending the Time War for those reasons.
4) He is wearing an amalgamation of clothing that was worn by 2 Doctors...both of which happen to bookend the Time War period.
He is the Time War version of The Doctor.
These are all really good points I find hard to argue with. But I still will, because it's the internet. 1) Yeah, probably, but I bet there's a little leeway in this. Like maybe, because all the Timelords are dead/temporal locked, he's the only one who knows what he will truly become. 2) shit, yeah, that's actually a good point 3) I kinda thought the same thing when I heard it. It's the version of the Doctor who "did what he had to" to end the Time War. 4) I had noticed the jacket and the vest, but hadn't put 1+1 yet. That's a pretty good idea, but the Doctor, generally, 100% changes his style between the regenerations. Doesn't mean he did, and this can't be him, but still. Basically, the more I think on this, the more likely it seems. But I still
wanthim to be the Valeyard.
Also (and I know a few have touched on this), it's interesting to consider Matt Smith as the 11th Doctor...with a little asterisk next to it, saying he had one regeneration that wasn't the Doctor (he said he wasn't, that the name was wrong or whatever, but that intro text said "The Doctor" throws me off).