Not that I think that would be bad, but Momoron already had that backstory and he, while useless, does not even begin to detest pirates the way Akainu does.
I am kinda hoping Akainu's backstory to be more personal and involving, imo. After all, he already looked bloody and vicious even as a kid.
With his absolute justice view and his unreal hate towards pirates, I hope his backstory is like:
- His parents/family lived in a peaceful town/village and ran an orphanage/institution/hospital that acted like the Red Cross in real life (neutral, helped everyone out). Basically believes that everyone deserves a second chance.
- One day, they took in a pirate who was heavily injured. They nursed him back to health...only for him to overpower them. He turned out to be a pirate captain on the run from the Marines. Worse, he alerted his crew of his whereabouts. They came for him.
- For days, Akainu, his whole family, their hospital/orphanage, and his whole town/village were tortured/raped/abused, but not outright killed, by the pirate and his crew.
- Akainu asked why did the pirate do this after having been helped. He answered with something, "We're no saints, buddy. We're fucking pirates. What do you expect?"
- Akainu's parents/family saw a chance to smuggle him out, did so successfully, and got him out. This cost them, however, their lives.
- This permanently marked Akainu's black-and-white view of the world and, as he grew up on the streets, made him vicious toward anything he considered unjust or risky toward the greater safety of the world (thus, his treatment of Ohara).
- Somewhere along the way, he trained every day and later obtained Magu Magu no Mi. At 26, he joined the Marines. The Absoute Justice doctrine of the Marines suits him perfectly.
- After he rose enough ranks, he hunted down the pirates who ruined his life and killed them all. However, he realized just killing them was not enough because pirates are everywhere. This caused him to further adopt the AJ doctrine to become the guy we see him as now.