People like to say earthquakes, but that can't be true. :P
Looking at the placement of the gym episodes, Iris & Drayden episode, the Pokémon League and Episode N, I think several things are actually hastily altered Black & White 1 stories.
Ash gets his 8th badge about 3 episodes after his 7th, so it's quite obvious to me that the abrupt Virbank City detour was thrown on top of the original Best Wishes plan late enough. If you remove this badge, perhaps moving Iris' episode forward a little bit as a result, Ash could have been challenging Drayden after a decently paced gap. Challenging a gym leader twice or having two characters take on a gym leader is nothing new to the show, so turning Opelucid into a two episode stop would have worked fine.
The Pokémon League could easily have always been planned to air around the point that it did. Isn't it a bit convenient that N and Neo Plasma are introduced immediately after? What if the original plan was for N to interrupt the league like in BW and bring back the original Plasma team for the first time since the Meteonite arc? Airing the missing episodes or just altering it to make it their first appearance would have worked fine in terms of the earthquakes. The fact that parts of BW1's story with N, Reshiram and Dragonspiral Tower made it into Episode N makes it seem like it's altered from the original overall series plan.
In terms of Team Rocket, aside from maybe some mention of Plasma or the Meteonite to connect the Meteonite and two Kami trio arcs together, I feel like nothing really changed with them. Maybe they would have involved themselves in the original N plot like they did in the one we got, but that's it. The World Tournament Junior Cup could have easily been a Don Tournament. In fact it pretty much was a Don Tournament with a couple of bells and whistles to promote B2W2.
As for Decolora Adventure? They could have easily used Eastern Unova, White Forest and Black City for a filler arc since Best Wishes was always meant to be faster paced and shorter than DP as far as I remember. But since they used it all up for the Black 2 and White 2 promotion, the Decolora Archipelago was born.
What do people think?