You don't need to muddy the waters by making Starfleet officers conspire with the Sona to make it a moral grey area. That comes from the fact that the Sona are trying to do something that will benefit millions of people. Is it right to prevent that just to benefit a few hundred Baku? THAT is where the moral dilemma comes from.
But what motivation do the S'ona then have to give the radiation to millions?
Profit, pure and simple. Hell, the story could have worked with a group of Ferengi.
The Ferengi are studying the planet. They've told Starfleet they are there for a scientific mission, but they're really after the profit from the fountain of youth. Starfleet gets a bit suspicious of the Ferengi after a while, and they send the Enterprise in to check things out. The rest of the movie can go very close to the way it is with only minor changes.