Dragon is fighting against the World Government, NOT the Marines, who are just their lapdogs and have actual people fighting for justice within their ranks, so it wouldn't make sense for this matchup
Sabo would just be another Ace but slightly better, pretty boring and lame if you ask me, especially because it has already been confirmed that Akainu's DF is superior.
Blackbeard has no deep beef with the Marines either, and he has more reasons to fight Luffy, Shanks or even Imu than the likelihood of him ever meeting Akainu face to face, so no.
For Aokiji, rematches are boring and unnecessary, especially if the original match was OFFSCREENED and had a CLEAR VICTOR... nobody would want to see this till we see the first fight in full length first (which Oda will never do anyway)
this only leaves Luffy as the most fitting candidate since Akainu has:
-killed his brother
-gave him his trademark scar (which itches to this day)
-specifically targeted his life throughout Marineford