Killer and Zoro will follow their captains. So the match-ups will be determined by Kidd and Luffy.
The problem is Kidd also said he wants Kaido, and Big mom says she wants Luffy. It could be a mixture, Kaido fights Kidd, then Big mom attacks Luffy, Zoro tries to protect Luffy, while Killer protects Kidd. Law will be crucial, his DF power is perfectly designed for team battles, they already made combos with Luffy against Doflamingo, if I were Kaido or Big mom I would take out Law first because of this. Law can both save people from getting hit and he can create openning for others to hit, he has an incredible power for team battles.