So upon Naomi dropping the bomb at the end of D.O.C that there were no survivors of Oceanic Flight 815, I got to thinking.

Ben had access the news from the outside world due to Mikeil and his satellite station. So he'd probably know the fate of the people on that plane. Knowing this why would he let Micheal find rescue?

Everybody is dead and then out of nowhere a father and child come back from the dead and say they've been trapped on an Island?

You could assume that Micheal made up a story possibly diverting people from coming to the island since he doesn't want anybody to find out about what he did to get Walt back, however I'd like to think that this would seriously debunk the crash findings of the oceanic Flight.

So what I'm guessing is that Ben send Micheal out to a certain spot only with the vague promise that he'd "find rescue", indeed he probably found rescue, but not the kind he thought he'd find.

What do you guys think?

I think your stating the obvious, everyone knows they would not let them go.
For a start we saw the stuardess and children still on the Island,
the others were fasinated with Walt the wanted to keep testing him
and they would be a liability (as you stated) to the secret experiments being conducted by Dharma/others, and all of the plane crash survivers ARE test subjects.
I think I made my point.