First of all, if what they depict is accurate, there is no basis for a defamation suit. Second, as "public figures" the Bidens would have a steep road to climb to establish invasion of privacy or similar claims, or even defamation claims. Not to mention that there appears to be quite a trove of publicly available court documents relating to Hunter's various depravities.
Although it is also true that anyone can sue, even without a meritorious claim. With the corrupt judiciary that we have, the Bidens might sue. But I think it would be a mistake. The suit would give more publicity to the film and the information that would come out in the discovery process would be stunning.
First of all, if what they depict is accurate, there is no basis for a defamation suit."
Pretending to quote someone without actually quoting them is never "accurate." Maybe the film shows a disclaimer saying, "None of the the dialog in this film was ever spoken by any of the real people who are represented by actors in this film. We made it all up." Would that be good enough to prevent a lawsuit? I am imagining a film by Michael Moore in which actors playing Donald Trump and Vladimir Putin are shown talking on the phone about hacking the 1996 election. Would a disclaimer at the beginning of such a film be enough to prevent Trump from suing and winning?
The suit would give more publicity to the film and the information that would come out in the discovery process would be stunning.
That is almost certainly right.
What other films have put dialog in the mouths of public figures who were alive and active during the film's production?
This seems unusual to me, but maybe it is not.