If it's to recruit, which of the Shichibukai do you think is most inclined to join him? Weevil is the only one that comes to mind.
Weevil is the only one that could work, if at all. The others certainly would not submit to anyone.
Same for their fruits, Hancock's is like the most terrible misfit for the Blackbeard Pirates, and Oda won't kill Buggy just to rehash his fruit, that's not the payoff Buggy is set up for being one of the most recurring characters in the story.
Given how the Marines are already involved with the Shishibukai, I doubt that is what Blackbeard is going for. The idea of trying to recruit Hancock or Mihawk or Buggy just doesn't sound good.
The only characters with a very huge risk of getting killed for fruits are Crocodile and especially Daz Bones. They are in the New World and have powerful fruits, but no plot, not even foreshadowing for one, and are completely expendable in the grand story.
Other than that there are few, especially because Kaido's zoans are uninteresting to rehash, and Big Mom's food dfs are useless outside the hands of dedicated chefs. I mean technically he could attack Buggy to get Galdino's or Alvida's fruits. Alvida's for Vasco Shot? Hm...
We also have to keep in mind that the majority of the Blackbeard Pirates already have fruits so Oda won't go too wild. I think only Burgess and Augur definitely have no devil fruits. Shiryu, Laffitte, Devon and Wolf already have one. Q is likely to have one, and before Morley was introduced there was a theory that Pizarro was behind Level 5.5 and could transform his hands into drills, I still think that or any other kind of fruit has some merit as Pizarro wore very unusual clothing for someone that was supposed to be in a cell. Vasco Shot is completely unknown, we really know nothing about that character.
So there is likely two or three fruits? Maybe we should extend the discussion to that?