B isn't exactly a big timeskip either, guys. A few immortals could get to China pretty quickly, even with Bronze Age tech.
"We no longer have any eyes on that world. We still haven't repaired the damage those damned pests did to the link."
"There are other ways to observe. May I be put in charge of this project? I am sure all of you have greater things to tend to."
"... very well. You now have responsibility over this world. Don't mess up like he did."
"I won't."
There are no avatars on Earth, but the Masters have "other ways to observe". They are guiding Ean against the Terasphagos and learning more about him through the Northern Kingdom's forges that they set up, which serve as their "other ways to observe". The Northern Kingdom arose at 2,000 B.C., right around the time that we woke up from our coma and defeated Sekhenun:
The North:
Far in the cold north, there appears to be a rising power that has united the squabbling tribes. More and more Gieloth are starting to venture there, attracted to the growing civilization.
The very secretive power behind the North is not an avatar, but an immortal, albeit one who is closely attuned to the Masters. Possibly Naram, possibly someone else similar to him. As far as the tech on masonry, it was obviously something that they leaked to our spy on purpose. They're letting us have it so that (a) to help us beat the Terasphagos and (b) to observe us more easily. I get the feeling that there's also another hidden price tag here as well.
Nothing is free and the masonry upgrade is cover for something else - just like our initial trade agreement was cover for observation. They know about our spies, of course, and they're using the Watchers as yet another way of keeping tabs on us. This reminds me of the foolishness of zapping Marduk with Zeus' thunder and how it was a bad idea because it was too good to be true. Here is a hint:
It looks like you would have to emphasize that your watchers know that initiative was important, but too much initiative was dangerous - this was the risk of letting them operate independently for too long, effective though it was.
If we start using Northern masonry to build our wall, it'll encourage our Watchers to become bolder, which will make whatever we do even more obvious to the Northerners. My recommendation here is that we shouldn't take the free lunch unless we really need to (i.e. we leave for China) or we want their guard down (i.e. going North).
If we pick A, defending ourselves from the Terasphagos from Korinthos will be much easier than doing so from the miasma anyways. Luckily, we've also lost relatively few men in our army during the retreat, so our army came out mostly intact as well. Unlike in Olympus, we're able to see where they're coming from much more easily, and we have Athena with us this time, which makes organizing a defense much easier here.
More importantly, (2) will start forcing the Northerners to begin revealing themselves a bit more. They're desperate to give us their tech, so I think if we refuse their offer here, they might reveal more of their operations/motivations. Thus far, we've been taking everything that the North has offered us, so I believe that if we change up the dynamic for once, it'll force them to put themselves in the open a bit more. We need to find the hidden hand guiding them, and we aren't going to do that by blindly taking every offer they put on the table.
China
"The immortals and the Gieloth have a ceasefire. The Yellow Emperor apparently came to some sort of agreement with the Gieloth."
The Gieloth here have some sort of trump card. We know that they're going to be creating the Tree soon, so they must feel confident that they're going to win. If we were to go to China right now, we'd save quite a few immortals and possibly earn some allies to take back to Greece with us.
Voting A2 for now, but I could be swayed to B1.
A1 
Now I know how mad prophets felt. Now we either royally screw China up, or royally screw our Empire up.
It's Shulgi gone Loki. He's made the voices his bitch and gets the advanced tech from there. He also wants the masters out of the equation, and he doesn't want Earth to be blasted to hell. He doesn't trust nor like Ean one bit on account of him killing him earlier, but possibly we can put those differences past us, should we meet and have a chat..
