Akainu, Robin, Blackbeard and Buggy were all changed too much. They should have basically looked the same post time skip. They're not teenagers who change how they look late into adulthood
Yea Akainu's preskip design was just too raw. No cigar, clean shave to show off peak jawline, it screamed he got down straight to business.
But I guess it was appropriate now that he has a desk job, the design needed to reflect this. You can literally tell by looking at both designs which one is built for chasing down pirates like a mad dog, and which one is sitting on his ass doing paperwork.
Kizaru's design didn't change cause his role was the same.