WHY did Dougherty bother with this convoluted kidnapping scheme?
It difficult to think of a reason, the Baku should have been openly approached, the situation laid out and told to get their things together.
But consider this. The Baku were able somehow to force the Sona off the planet, and prevent them from returning later. While living a simple life, the Baku weren't a non-technological people. They were able to diagnose the phase variance in Data's positronic matrix, as being the source of his problem.
While he didn't know of the Sona expulsion, Admiral Dougherty may have been apprehensive as to possible Baku abilities.
Sigh, your never going to get that this is the Federation not the Terran Empire are you?
Fail to see your point. Remember, from the Federation's point of view it's primarily about the medical properties of the particles in the rings. Not the Baku, not the Sona, not even the planet itself.
The whole purpose behind removing the Baku was so that they wouldn't be harmed when the particles were harvested. If it were up to the "Terran Empire" the Baku would have been left where they were and allowed to died from the heat created by the harvesting. The Federation didn't want them harmed, and neither did the Sona.
Moving the Baku to another planet is going to help billions upon billions of people, when are you going to get this?