I think all the above will be sufficient in adding flavor. It's going to boil down to how you prepare beans. I, If I plan accordingly, prefer to slow cook pinto and navy beans without soaking. I'll toss in hocks, brisket, belly or whatever I have in the freezer in the crock pot then add onions, chipotles, bells etc. I then add the beans and pour in simmering stock and water.. This gives whatever bone-in meat plenty of time to break down and time for the marrow to cook out as well..
This is exactly why I buy shanks and ox tails. They are cheap and I can smoke them up to 145-150, vac seal and freeze until needed for such purposes. I've yet to do anything bone-in in a gumbo but I'm not against it at all..