He didnt mess up anything. Akainu's military is a separate thing that deserves focus when Akainu is involved, because thats the military force he built as Fleet Admiral:
D: Odacchi! Ello. So Marine Admiral Chaton, who asked out bombshell sexy dynamitz Momousagi from the SBS on page 86 of Volume 74 100 times and got rejected 100 times looked something like this, right? (→) P.N. The Hide-yan with the red hair
O: Uhhh. So since he can't possibly be one of the admirals... Oh, it must be that dude, right?
The guy that, like Momousagi, was nominated to be an admiral; this (→) guy, Vice Admiral "Chaton", right?! You're right, you're right, I found him in my sketchbook. There actually was a time at one point where I considered making the new admirals a "Pig" and "Kappa" to match the "Monkey" "Pig" and "Kappa" trio from Journey to the West. However, in the end, I decided against it and we're here now with our newest additions, the "Tiger" and the "Bull".
There is an actual reason for this, but I won't tell.
Oda evidently wants to deal with what could be considered some of the older remnants of the marines before the Zodiacs come into focus. When you have Garp, Tsuru, And Sengoku retiring, Kuzan leaving and Kizaru losing, you are left basically with his new force.