They'll probably tell you that Hayter was too busy voicing Raiden.
Not TeamA but I think because Deja Vu is sort of meant to be a mix of old and new. Like you start it without the "skins", and I'm pretty sure I heard Kaz call me "boss" when playing it even though you hear him voicing Solid Snake's lines but then you also have Downes imitating all the other voices from MGS1 instead of using actual sound clips from the old games.
I see.
Another problem I have with the Hayter theory is that it would make one of the biggest "surprises" region exclusive. I find it weird Kojima would go through all this trouble just to give the Western audience an exclusive surprise. The VA didn't change in Japan. When you do a surprise like Raiden in MGS2, it affects everyone.
At the same time, if it were true... Kojima wouldn't change the JP VA. If he would switch both Hayter and Akio Ōtsuka, people would know something is up. The Hayter "asked too much money" argument is plausible, but people would know Kojima is fooling us if he did it with both VAs.
Now, team A assumes we'll see an adult Solid Snake at some point... right? Hayter can't voice a teenager. Even if it would be hilarious. Thing is... that would mean Solid Snake gets a different JP VA. Don't think we'll see Ōtsuka play Big Boss AND Solid Snake in the same game. That didn't happen in MGS4 either. You could argue they'll just use a different JP VA for the Japanese SS and use Hayter for the Western SS, but that just seems... weird to me. Then why didn't Hayter play Big Boss? I mean, unless Kojima is doing a gigantic troll... you'd think SS only appears near the end. That means Hayter would have a far smaller role than the previous games. Why would he have a smaller role all of a sudden?
It just doesn't make sense to me. I have no doubt Kojima is planning some kind of surprise and it wouldn't surprise me if Solid Snake does show up... but it wouldn't surprise me either if he wasn't voiced by Hayter and that Hayter isn't even a part of MGS V.