How I see it, think Oda will be slowly revealing Dragon like after every arc or so until we finally reach the arc that involves Dragon himself. Well Aokijo been recommended by Sengoku the current fleet admiral to be the next. Akainu is good choice some what, I honestly think he's the admiral with the least control . Only reason he will be controlled real good with the elders since they too some what share his dark justice idealism. But for me honestly Akainu should be kept a admiral, if you gave him the fleet rank is like putting the red dog on a leash. He needs to be out there barking up justice in the new world. Think that will fit his character better, than sitting at HQ giving orders. Got to agree with Coby and Helempo, I also think they will end up under Smokers command. This first came to mind when Oda drew a cover page with Tashigi teaching Coby. As well many other story element reasons I have, but won't rant off about it.
I too want to see ship battles, the war showed us so many cool looking pirate ships. Be a good way to show off the new sunny. Speaking about that I think Franky will learn some insane technology from Vegapunk besides improving himself but the sunny as well. Be funny if Franky is able to connect himself to the sunny, like wirely. Then the sunny starts transforming into Gundam Franky!