You might want to cut a little on the mob-wiping part of the battles and concentrate on the meaningful fights. You write great fight scenes in general, but having the same one five times in a row (for each important character one after the other) at every battle can get a little repetitive after a while.
To quote the Knight of Five, "You can only stomp tadpoles for so long until redundancy sets in!"

Story is still as amazing as ever, I'm slightly disappointed that Tianzi hasn't yet reminded her soldiers that any of them who survived Xiaopei, herself included, should be thanking the BKs and Zero instead of scorning them, even though his plan didn't work as well as intended. Like, it's obvious they're just annoyed at their own powerlessness and jealous of the BK's strength, but still, venting that on the rescuer is about as low as you can get.

On a technical side, you use "he/she exclaimed" quite a lot in your dialogue, and not for sentences that, in context, seem spoken in a particularly loud voice. It's a bit weird and unsettling, honestly.

On the other side, I love myself a good speech, and holy hell do you deliver on those! Really liked the parallels between Liliana's intentions and the Zero Requiem too. Seems like she understands Lelouch's nature better than most.
I suppose the "Mercury" link between Lelouch and Kallen's chosen music was voluntary too? Nice touch.

"One does not take on an enemy like Britannia over a single life."
Hmm. Orange Incident. Prison attack. Pendragon Siege.

Bloody hell, how long I have waited for someone in story to finally denounce Suzaku's bloody hypocrisy. Just for that, you have my thanks (well, the rest of the story is bloody awesome too so don't think it's the only good part either).

Are the twins Shamna and Shalio? Does Zilkhistaan exists?

I...this...am... Holy shit
Holy shit.
I'm overwhelmed. How the hell could i've missed this bangers all these years?
First, op tsunami and lelouch vs suzaku (goddamn that's a wham line), PLUS Izumo trashing three-carrier fleet, if you can add some tactical fuckery for any next naval engagements like the one i've read in some Halo novels that would be soo perfect.
And then there was Red rebellion...
Holy shit. If only this was R2...
Aand next, the incursion to the far east and some good payback to the eildons!

Your story is very good. But there is one thing that I think is wrong. You are not killing villains. If Lelouch wants to win the war then he must kill his enemies, no matter who they are, otherwise they will keep coming back to try to defeat him. Also where are the other main Eildons. Where are Richard, Thomas, Sharon etc. Is Leila against Lelouch or on his side? Will Jeremiah stay against Lelouch? Will the U.F.N. be created? And when is the next chapter coming? I really want to see the Black Knights fight and defeat the Eildons. It will certainly be interesting to see what kind of technology the Eildons use. By the way, good work with the Eildons and the European Union. In the anime, I always thought the E.U. was underused and I still wonder how the Geass Order was so easily destroyed, that made no sense to me, that cult is centered around the power of Geass and was led by V.V and Emperor Charles, how could it be wiped out so easily.

Good Lord almighty, this story is incredible. Not only do you retain the flavor of Code Geass, but you build on the world and flesh it out so magnificently that I can't help but be in awe. This is such a fantastically good story and I can safely say that its one if the best I've ever read!

Great chapter! I can't wait to read more!

I get the feeling that when Britannia is defeated that the remaining Britannians (that manage to survive the war) will be sent be to tried in this universe's version of the Nuremberg Trials (or trials similar in scope to the Nuremberg Trials).

Fire Emblem Awakening and Sword Art Online crossover

Snakeboy33 has a point in the logistical effort of invading mainland Britannia proper, considering its the entire Americas continent surrounded by two oceans. Even with the support of the Chinese Federation, the EU (after nationalists are defeated), and other factions; amassing a large invasion force to directly invade mainland Britannia is going to require a massive organisation and buildup that's going to take awhile considering all other Britannian armies that needs to be defeated first.

And Britannia itself still has craploads of resources and forces that invading it is going to be costly, along with a massive landspace to cover and occupy. Though I suppose the capture or destruction of Britannia's sakuradite source(s) is a factor in that as it would seriously hammer Britannia's military machine.

If war was only fought on the battlefield and not behind closed doors, we would've destroyed ourselves ten times over throughout the history, hence chapters like this one shows us the importance of diplomacy, behind closed doors talks and that not everything revolves around going around and blowing shit up. That said, we finally get to see that Orpheus is still alive and kicking, caught me completely of guard that one, nice.

Rommel shows us again that he's earned that title of General not only with using brute force and/or sucking up to others like certain characters.

If I didn't know any better, I'd say there's something poetic in both Lelouch and Orpheus putting emphasize on their queens... Although, we need to see who (perhaps 'what') is Orpheus's queen.
And our macabre super-secret group is gonna make a big move soon if all points to that, hmm, yet I personally am intrigued about that Knightmare meant for Jeremiah. It's not a Giga Fortress, right? That'd be pretty, well, bad tactics, since I think something with that size and tech is not easy to produce and should be used by a highest positioned person within the organization and Jeremiah, however useful V.V finds him to be, is definitely not it. But hey, still works for me at the end.

I feel like the discussion of invading Britannia proper warrants more discussion, if only from a military standpoint. Britannia spans most of North America, which is a large continent, and is separated from the rest of the world by two massive oceans, with the exception South America, and even then it's only connected by a narrow strip of land. It also has a large population which is (I imagine) not going to be very welcoming to the Black Knights; how would they deal with that population? Lelouch seems to talk about visiting upon Britannia the same destruction they imposed on the world; so does that mean they're going to occupy and subjugate the population as the Empire did to other nations? Ethics aside, that would be very difficult from a logistical perspective.
I just feel this all deserves more discussion.

Rommel is my favourite character.
And I liked that little tease Lelouch was throwing at kallen.