That part where Picard beams down alone and asks the Baku how old they are, and then right after the conversation with Dougherty. Why doesn't EITHER of them suggest during the conversation, that now that contact has been made with the Baku already, that they should just go ahead and attempt to negotiate?
Who would be suggesting what to whom?
Picard is outraged that the Ba'ku have been victimized. He wants an immediate end to that, not any silly negotiated compromise. As far as he knows, Dougherty is a criminal, and by reporting to his superiors, Picard can get Dougherty thrown to jail and the Council to start talking with the Ba'ku.
But then comes a surprise twist: the Council thinks the abduction plan is fine, Dougherty is the hero and Picard is the villain. Who could negotiate with the Ba'ku now? The Council? They are not interested, as far as Picard can tell - at least until Picard can get a message out of the Briar Patch and sort things out, but that's a slim hope if the Council really is as villainous as it seems. Dougherty? He's certainly a villain. Picard himself? He is a lowly Captain who has absolutely no say on what happens to the Ba'ku. Not unless he uses firepower to gain a say.
There is nobody to negotiate with. Picard thinks there might be, but Dougherty straightens it up for him: the Ba'ku are allowed no say, because of course they would say no to the scheme that has already been declared to be a workable one.
The writing is subtle and clever on that. UFP Council made its decision under the delusion that the Ba'ku were primitives who could not be contacted and would not care. Picard tries to point this out to Dougherty, at which point Dougherty says he doesn't care. So Picard finally knows exactly what to do: one, inform the Council of the real nature of the Ba'ku, and two, stop or at least stall Dougherty who most definitely is a villain now, having openly stated that he still sticks to the original plan in face of contrary evidence.
It's the fault of the Briar Patch that negotiating THERE and THEN will get nobody anywhere - all the parties interested in talking with the Ba'ku are on the other side of the Patch. And negotiating LATER will only happen if Picard fights back Dougherty with arms.
So, not a plot oversight, but a carefully spelled out plot element.
I'm not suggesting a negotiation with the Federation Council, I'm suggesting a four-way negotiation between Picard, Dougherty, the Baku, and the Son'a. It's the obvious move after the holo-ship deception is revealed. Whatever Picard thinks of Dougherty is irrelevant, all diplomats negotiate with people they don't like. Maybe Dougherty would say no, maybe the Baku would say no, but the fact that it's not brought up as a possibility is just silly and a clear recognition that the plot is built on a house of cards.
You only think it's built on a house of cards because you don't see how the Ba'ku could say "no" and still appear sympathetic. But that's easy.
"Excuse me, but would you be willing to negotiate for the Federation and Son'a to have access to this little Fountain of Youth you've got here?"
"Uh, you mean the same people who spied on us, disrupted our village, and were going to secretly steal our planet out from under us?
These are the people you want us to negotiate in good faith with?"
"Um, well. Yes."
"What kind of morons do you take us for??"
The Ba'ku had no reason to trust Picard or the Federation after the shit they pulled, and frankly they would've had every right to tell them to fuck off after the deception was uncovered. Why negotiate with people who were obviously willing to use underhanded measures to get what they wanted? (Not to mention, they knew the true motives and identity of the Son'a, who did not
come back to reconcile, but to uproot/murder their parents.)