I kind of agree on some levels, but look at this panel of Akainu after he fights Kuma: he looks like he's contemplating the past, IMO. Like, this is probably the most pensive and thoughtful we've seen Akainu in the series.
If Hibari is Akainu's daughter, this would make Akainu's interactions with Bonney and Kuma much more meaningful.
Akainu's flashback to his discussion with Bonney makes it clear he's aware of Kuma's circumstances, as well.
Kizaru has already gotten a lot of characterization in Egghead, I think this would be a great chance to dig deeper into Akainu's mindset and past.