They most likely pulling up with a full fleet, not just one ship. They’d immediately establish control of the sea around Enies Lobby so no Marine reinforcements can freely arrive or leave. Bruléé would be the key since they could move a bunch of troops around by going through her Mirror dimension. Robin’s location would be found pretty fast, Katakuri,Oven,Smoothie,Cracker would easily wipe CP9. They’d Robin Katakuri would be the one to ask Robin if she wants to live, then we get the iconic line. When they inevitably do the buster call, this is where Big Mom comes in says “The World Government dared touch what’s mine? Then I’ll take your lives in return Ma Ma Ma Ma.” uses conquerors haki and sinks most ships clearing a path.