Storywise, I think removing them won't affect much to the game's story mode, BUT gameplay-wise....
I could never understand why did everyone want good chars to be removed?
For Justice, Kliff and O-Sol they will return as DLCs, but why remove Slayer, Testament and Robo-Ky??? LOL they are some very good chars to use, and they do have a nice background story... What are you thinking?
One should always consider what's good and what's not....
I'm looking forward to seeing the Overture chars in Xrd though... They have some really good designs. (LUV Valentine , she ressembles Rachel in many parts )
EDIT: You forgot That Man and his 3rd servant.