Dude there’s zero chance Oda gives Sakazuki a bounty 1 billion berry above shanks, let alone 1 Billion + Above someone he went 10 days against.
Bros getting 4 billion
Bros getting 4 billion
As far as I am concerned we can bet on Dragon too. That should show you that Is not the fact that we are talking about Akainu the problem.
Not to be rude, but it's your problem only if you can't accept Akainu is a future Luffy opponent and command a force that dawrfs Shanks' or any onther pirate for that matter. At least hypothetically.