First off, all speculation is just that. Don't take anything I say as fact.
But, here's the way I see it. If this is the Earth, the first thing that I find interesting is that there doesn't appear to be a Guild. We know all the different Presters had Guilds that were supposed to guide the various Presters (boy, I wish they had come up with unique names for these colonies instead of calling them all Prester
), until everyone could return to repopulate the Earth. I haven't heard much (or anything), of what was supposed to happen back on the Earth though during all this time.
It wouldn't be a stretch to think there would also be a Guild left on Earth to oversee its recovery. But, in the present, we're seeing what looks like Guild members in the role of the Adess Federation's Presidency and Intelligence Office. This suggests to me that if there was a Guild on Earth, then it fell apart some time ago and the descendants may have spread to the various nations on Earth, each with their own goals, dreams, etc. Having sat on all that technological know-how, they would probably find it easy to gain positions of power.
Of course, it's also possible that one of the other Presters had a healthier relationship between their Guild and colonists, and that they never lost the ability to use Exile to travel between their Prester and Earth. So, it's possible Adess and Turan are descendents of colonists from another Prester that made it back to Earth well ahead of the people of the Prester the first Last Exile was set on. Once back on Earth, there was no need to keep up the Guild/Colonist separation, so the Guild was dissolved and its members merged with the populace.
As far as the pilots that look like Guild members in the OP, I doubt they are members of the Silvana. The Silvana crew looks like they wear far darker outfits in the OP. Maybe the Guild is still around. Maybe some members didn't want to break it up and keep it going in a far smaller, third-party guerilla outfit that might stand in stark contrast with the all-powerful entity we are used to from the first series. At this point, it's all speculation.
Though, like you, I almost thought that was supposed to be Tatiana for a half second.
I also toyed with the idea that was Claus in that picture you posted (on the left).
It's a fool's game though to try to identify people while they're wearing a helmet.
And, I know others would like Claus and Lavie to show up, but I can't help but feel that we'd enter the problem of Gundam Seed Destiny, where the former cast ends up overshadowing the current cast. I'd prefer to let Fam and her crew have a chance to shine in the spotlight without that worry. My wish is for Claus and Lavie living a happy life on their farm, completely isolated from the problems of the world.
I'm wondering about Liliana's flashback where we see the former Empress of Adess behind a young Guild member. It would seem to hint at a time prior to relations souring between Adess and Turan. As for the young Guild member (even if there is no Guild, I'm gonna keep calling the albinos Guild members), I wonder if he was supposed to be Luskinia. The OP hints that Liliana is going to eventually submit to him (whether she does it of her own free will or not, we'll have to see), and he seems to have wanted her alive for some reason. I think they may have known each other, and she may have even liked him as a young girl is wont to like a handsome guy. Certainly, the OP has some symbolism going with Liliana laid out at Luskiana's feet with her hands reaching up all over his crotch. With a few wardrobe changes, that'd be a scene straight out of a Calvin Klein commercial.
There is Greek everywhere, but I am far too lazy to bust open the Greek alphabet and translate it all. If someone OCD enough to do so doesn't show up by episode three, then maybe I will.