Could someone get fast reply enabled on this forum? It's a real bother to have to go into formal reply mode.
Anyway, I looked through the previous posts, and didn't seem to see this anywhere, so I'll spew.
What really interests me about Code Geass is the analysis of Enlightenment vs. Japanese (and perhaps in the future Confucian? Who knows.) thought, and the issues that come up when the two butt heads. That and the complete despair that permeates pretty much every other episode. When I was watching it, I half needed the next episode, and half wanted to just stop completely. The actual geass part of it is really a third wheel to the series.
So . . . what happens if we cut the shit? We can keep in knightmare frames because they make battles go faster.
A. This would just make things easier, it's not necessary at all: instead of telling the king that he disinherits himself, he asks the king that he and his sister be hidden from the rest of the world so that they can grow up before being thrown to the lions. Maybe the king says something like, "The lions would not give you that mercy" and he says, "If a lioness is killed, then the other lionesses move in to raise the cub in her stead." Blah blah blah, long story short, he is considered a noble by the king so that later he can be a knight. If you wanted to, you could have him become a knight through guile instead of doing this, which works too.
B. Lelouch rescues C.C. again, but she's just a regular girl this time, maybe one who knows too much. She is shot in the head, but it's not a killing shot. He needs to use trickery and guile to get out of the situation that he is in, and pulls his "I am Lelouch di Britannia" card, and they're like, "Oh shit, call a knight, we have to keep him safe especially since they're bombing the country. Keep it secret, this is of the utmost important to national safety." They get Villetta, someone gives him a gun for his safety just in case. They put him and C.C. into the Knightmare with Viletta, he kills her and co-opts the knightmare. Using the knightmare, he kills the rest of the troop, and goes into position as we had seen before. He saves Kallen, but the rest of the troop dies. The two of them escape, but without his geass, he can't get close enough to clovis to kill him. He decides to become a knight so that he can get into a close enough position to his siblings to kill them, while staying in a position where it makes sense for him to carrying lethal weaponry.
C. Suzaku . . . well, Suzaku survives, but since Zero isn't helping them kick ass, there is no need for someone to pilot the Lancelot. He gets in the cockpit, and is told that he has great synchronization, but Clovis says, "No Eleven will pilot the Lancelot." Suzaku meets Euphemia, but because he hasn't piloted the Lancelot, he is of no interest to her. Basically he is unable to rise any higher in rank than Warrant Officer, and just by rising to the level of Warrant officer (unprecedented in honorary Britannians), he sparks protests across the country against Japanese. He despises this, but still tries to get promoted. He sees himself constantly passed over in favor of worse candidates for promotion, and eventually loses himself in despair.
D. Back to the academy: Lelouch trains like Suzaku, and eventually becomes a passable athlete. He gets good grades in school, and with the advice of C.C., who knows a good deal about how to start a revolution, although not sure why (amnesia from the shot to the head), she advises him to build a strong body of student helpers. He recruits Kallen, Rivalz (? I sort of hate him), Millay, and Shirley (I've actually always thought that Shirley was an underestimated character. We really don't see her that frequently in the show, but I think that if there was more good Lelouch fanfiction, I would be a Lelouch/Shirley shipper. Don't know why, I just like her.) Most of the underlying resistance infrastructure falls while he tries to get close enough to Clovis to kill him (this takes years), and the only member of the JLP left is Todou--the general tried to backstab Todou to save his own ass, so Todou decided to live instead of being betrayed, or something. I like that character too, but I guess he's expendable.
E. So basically, Lelouch is subtly gaining supporters, training them to be an indomitable strike force, and going through the ranks of the knights. They start small insurrections around the country, taking it back city by city, with each of the members of Lelouch's team leading double lives. Suzaku eventually becomes tired of the Britannian army, and defects to Lelouch's side.
F. Lelouch asks for an audience with Clovis, and has a robot pose as his personal attendant. When he and his attendant come in, the attendant immediately rushes Clovis, killing him just as he recognizes Lelouch. This can be done in other ways--an example would be that Lelouch convinces a fellow knight to ask for an audience, Lelouch says he will come along for moral support, pretends to get a case of the taco shits, slips in through a side door, and while the friend is talking to Clovis, comes in and kills Clovis and the friend, before going back to the bathroom. Anyway, Clovis dies.
F. They get back Rakshata, Todou, a lot of the old gang (except the ones who died) and eventually kill the rest of Lelouch's siblings, except for the ones who agree to abdicate their power, and in the last scene, Lelouch kills Charles and declares that he is the eighteenth ruler of Britannia, and C.C. regains her memory and reveals that Charles was a revolutionary in his youth too, and that the world has conveniently forgotten this Ó la 1984. We have an epilogue, and nothing has really changed, except that the Japanese have a slightly better position in life.
Anyway, this is just a basic idea of what might happen. I sort of hate Suzaku at this point, but you can have him succeed or do whatever you wish. It might be interesting to explore Refrain some more.
TL;DR? No Geass powers (for anyone), what happens?