JMS also claimed that if he knew that there would be a season 5, season 4 would end around "intersections in real time". And so most of Season 5 would have remained as is. Cut out Gaimans episode, the horrible one following the two maintenance workers and "The Deconstruction of Falling Stars" you only have to snip one episode from Season 5 as shown.
That doesn't really follow. If he sped up his original plan, then you have no idea where IIRT would have fallen into the original plan. It was the penultimate bit when we saw, it, but it might have been several episodes earlier in the original draft. All we know is that he intended to end the season with it.
He liked to use six and seven episode arcs, and you can seen examples of that throughout the show. He's also been fairly open about places where he intended to do it, but couldn't for whatever reason. F'rinstance, he said that had Sinclair stayed on, the mystery of The Line would have been revealed around 6 or 7 episodes in to season 2. Likewise, I recall him saying he'd intended to reveal Control about a third of the way into season 3, presumably as part of the ramp-up into independence.
My hunch is that the war would have ended about 6 or 7 episodes into season 5, leaving around 14 episodes for aftermath.
This actually is reasonably consistent with what we saw, as there are 6 or 7 useles standalone episodes in season 7: "Day of the Dead," "Secrets of the Soul," "A View from the Gallery," the Na'Toth one, etc. Take that crap out, and you're left with the 7ish episode Centauri arc, and the 7ish episode Telepath arc. Which gives us a pretty solid structure:
7 episodes of war, 7 episodes of uneasy peace, 7 episodes of the alliance cracking, but not quite crumbling.
Moving the telepath episodes up to the start really puts the whole season off balance from the gitgo, and all those 'why bother' episodes dont' help any. Basically the season feels really padded out, but if you assume a third of the season was the wrapup of the civil war, then it feels a bit more reasonable.