Well, the first couple of things that come to mind are that

a) Remember that Rand announced to his followers he wouldn't lead the world or the war, that he had other things only he as Dragon could do, one of them being fighting the DO. Rand did went to Egwene as if expecting her to play her traditional (third age) role as Amyrlin Seat. We probably underestimate Egwene's political role through the LB. She is more than just Amyrlin, she also stands at the center of the loose alliance of female channellers, and she is central to bringing together the nations at Merrilor to "oppose" Rand. Even if Rand sways her and the nations and WT follow her change of mind, Egwene now has positionned herself to be a central player/leader. It appears the nation suddenly wish to see the Amyrlin as ruler above the rulers again...

b) We are only guessing that the book with deal with the Fields of Merrilor meeting quickly. It's quite possible there's more build up to that then we think, or that the negotiating takes a larger chunk of the book than we think.

c) Don't forget the Seanchan, the Seanchan woman telling Egwene "we must help each other", Egwene facing Rand and with women, among them a Seanchan etc. The bets are open if the Seanchan will play a mostly disruptive role in TG or join the Light, but Egwene's obviously not done with the Seanchan - TGS was a build up to the final "confrontation", not the resolution of that storyline.

d) The reunification of the male and female Aes Sedai isn' complete, and nothing says this won't be a development playing out over the course of the LB rather than something that will miraculously happen at the beginning. Again Egwene might have a central role to play. The Windfinders don't really believe in the Cleansing etc. Another major factor is Logain, with whom Egwene has ties.

e) The BT issue. It's another major crisis Egwene is tied to as Amyrlin. She has many sisters involved there, the issue of the envoys isn't solved, far from it, not the least because her envoys are there because Rand told the AS to go there. Again: Logain. There's no certainty Rand will be the one to deal with the BT, or that it won't require big AS involvement, even in the decision making. It is after all partly a Rand problem and partly the result of Elaida's mess.

f) The Aiel and Egwene. The WO and the AS. Egwene going back to the Tinker camp in TGS. Enough said. Don't forget how exactly they served the AS, the Voice, their powers, what Singing could really do. People tried to get BS to give more details that are not in the BWB. Big RAFO apparently.

g) The most important of course: Egwene and TAR. Three of the remaining Forsaken are the most dangerous and skilled TAR users among them, you can hardly think it's a coincidence RJ kept the three most skilled there for the end... Graendal possibly, Demandred in a big role, and the "Dream team". One of those at least is confirmed as a full dreamer but Brandon suspects there's at least two, one of each gender which means Moridin is a Dreamer (well, it won't be Demandred). It's likely we underestimate the role Moridin's prophetic talent has had in the story (and backstory) and that he is the source of the Dark Propĥecies. Egwene's prophetic talent is only recently increasing. It will likely be relevant during TG, not only her ability to Dreamwalk. In a Q&A, Brandon warned not to underestimate Egwene or start believing Perrin is better than her just because in TGS/TOM she was rusty because she had too much to handle recently to work much on her skills. Lanfear once manipulated Egwene like a babe, and there's a strong possibility there's now unfinished business between her and Cyndane. Same for Moghedien, as a matter of fact. Egwene managed to best a Forsaken and destroy her mind, appears to have single-handly destroyed the BA (the Shadow might never discover how she did it) - Ishamael's pet creation, which Shaidar Haran tasked Alviarin to save in KOD. She played the major role in turning away the Seanchan attack. She has solidly in hand a group of what, 2000 female channelers - and has managed to undo nearly everything Mesaana has done. None of that should make Moridin see Egwene as a negligible quantity or for him to sit idly letting Egwene and Logain recreate the real Aes Sedai of old... And worse, the bloody woman is a Dreamer and has just proven to her own organization that she truly is one and her Dreams must be heeded. Egwene herself should now be fairy high on the Shadow's hit list. And that's without getting into all the possibilties that TAR could have a major role in the endgame or during TG itself. And of course, there's a dreamspike to take care of. Brandon kind of hinted that LTT was not quite in Egwene's league in TAR.. and after what happened to Graendal's one, the Shadow will certainly heavily protect the second one.

h) Egwene is the leader of the Aes Sedai. If Rand doesn't lead the war himself as it appears to be his wish, then Egwene's decisional role about the LB should be massive. Her storyline prepared her for that role. She's not been forced to learn to deal with generals, organize a campaign with one, learn to trust them and for them (well, him - Bryne) to trust her for nothing. Isn't it obvious? Mat has started to learn to work with Aes Sedai, and Egwene has learned the value of and to work with a general. None of that prepared them for working with each other (not to mention the last time in Salidar that didn't go exactly well...), which of course they will soon have to do on a regular basis, and which should be.... hilarious. Egwene will be on the war councils.

There's probably more, and some of that is probably of the red herring type that won't lead anywhere important in the end, but it's not likely to be all or nearly all of that that won't be.

About adding scenes, BS said that he wrote her he realized telling the story of what RJ had planned for her required more POV/scenes that he guessed before he started writing her.