But what would have been the conspiracy? The events in INS seemed pretty isolated.
That's how all conspiracies begin, with a seemingly isolated incident that's later discovered to be connected to something larger.
The fact that the Federation was condoning such an act is, as Picard said, a betrayal of the very principles the Federation was established upon. That can be definitely be taken further with a story that something isn't quite right within the Federation (with
Insurrection as the first act, a second act could reveal the Federation participating in some very un-Federation-like things). It's the classic "Do the ends justify the means?" moral dilemma.
Yup.
Nope. Actually, the only "conspiracy" Trek movie was Star Trek VI. The Genesis Project was a scientific project that became the obsession of Khan (and later the Klingons) for use as a doomsday weapon. We've had far more stories about trying to stop a weapon of mass destruction than anything else in the Trek films.
They are the law making body of the Federation. Many laws are open to interpretation and those that aren't, they could merely change.
So unless you're going to go down the path that a law making body can't create and change laws as circumstances dictate, you're going to have a rather dull follow-up.
Hell, it would be a dull follow-up either way.
I disagree.