User blog comment:Observer Supreme/Potential/What if Shichibukai/@comment-83.30.186.254-20161209214642

 1.  Ace has been offered the position long time before he joined whitebeards crew, and by the time of marineford arc he was probably much stronger. Also his bounty was 70 million higher then current highest bounty among shichibukai so it's more than enough, and his connection to Roger would definitely prevent him from joining (Akainu would kill him just because of that).

 2.  Luffy got the attention of WG only after he beat up Crocodile, showing incompetence of the WG and shichibukai, and then proceeded to declare war on WG in Ennies Lobby. No one employs someone who attacked him, so there's no chance for that to happen.

 3.  Basil Hawkins dosn't seem like a bad idea, but only if he got some major profit in it (imagine if he made voodoo doll of vice-admiral, he could kill two birds with one stone)

 4.  I don't think Akainu feels confident enough to attack Yonko on his own territory, especially considering Kaido's plans to start a war. Moreover except providing information Lola might not be that useful.

 5.  Vander Decken is not really strong and doesn't have a reputation like Buggy, so he is not much use for WG

 6.  I think you meant he wouldn't survive in New World. In my opinion if he just trained his haki some more and moved at the speed of lightning during fights he would be able to fight most enemies in NW. He would probably be the most powerful shichibukai and a good replacement for Doffy.

 7.  Pedro seems like a good idea although he might hate WG too much to work for them (I don't really know that)

Beside this from the Supernovas only Jewelry Bonney seems right, from previous antagonists maybe Perona or Absalom, but I really hope Oda introduces someone new and fitting for this role possibly around Wano arc (samurai shichibukai with a Zoan would be pretty cool).