According to Word of God, the original plan for Chapter 30 included a section where Yang would get mind-controlled by the Mad Hatter and nearly kill Batman, to add new angles to the debate on Batman's contingency plans. This was scrapped due to it requiring Yang to hold a massive Idiot Ball, and also coming so soon after the Poison Ivy mind control incident. The final chapter has Yang simply beating up the Hatter and then talking things out with a disguised Saturn Girl.
According to this post from trestwho, the original plan for the escape from Brainiac's ship was for Ozpin to tell Penny to escape, with Penny offering to bring Ozpin along, only for him to decline with the reasoning that Vale needed him to maintain its stability. This was scrapped due to realizing that Brainiac would not allow Ozpin to be out of the cities during such an attack, and after realizing that it would make sense for Qrow to be tested on as well, thus transferring the role over to him and having him escape too.
Originally, Booster Gold was the one to join RWBY on their wild west adventure, before it was decided that the Legion was a better fit.
from trestwho, the original plan for the escape from Brainiac's ship was for Ozpin to tell Penny to escape, with Penny offering to bring Ozpin along, only for him to decline with the reasoning that Vale needed him to maintain its stability. This was scrapped due to realizing that Brainiac would not allow Ozpin to be out of the cities during such an attack, and after realizing that it would make sense for Qrow to be tested on as well, thus transferring the role over to him and having him escape too.