Ryokugyu and Fujitora intercepting Cross Guild at Impel Down would be bonkers. CG breaks out Doffy and Weevil and probably some other toughs. Could even take advantage of a potential ruckus at ID while Marco was already on his way to scout out Weevil's imprisonment, mirroring the last breakout with the BB Pirates swimming in Luffy's wake. The THIRD Impel Down breakout happening on the other side of the world while the Egghead Incident has been going down is going to be so rad if it happens. Sand vs. Forest in a closed environment under the seaI think it will be about Cross Guild and Impel Down. It's clear that the Cross Guild is essentially going to be a Yonko crew formed from the former Warlords since they were the other great balancing power.
Knowing someone as strategic as Crocodile this all probably happened while the Navy was doing the siege on Egghead. An Admiral and all other available Navy resources were taken there so Impel Down wouldn't be able to get back up. By doing this they probably are going to get Doflamingo and as a bonus Weevil freed. And since Crocodile has been in Impel Down they know how its structured and operates making it less risky to attack.