For the warpout thing: You would need to create an event in the Events editor that triggers true only when an important objective is accomplished. From there it is simple to create a "traitor" debriefing (which only means you yell at the player a bunch and threaten court martial and stuff like that) that triggers if the event is not complete.
Alternatively, you could simply use the never-warp sexp to trap the player in the mission until a certain point.
What you are referring to as "objectives" are actually
directives, I think. When you make an event in the Events editor, you can also make a directive simply by putting stuff in the "Directive Text" box near the bottom. That text would then be linked to that event (an event's little bullet point will turn red if there is text associated with it). When the event returns true, the directive (in-game) will turn blue (hey, that rhymes!

). Anyway, you should be careful to link your event in such a way that the directive only appears when it is relevant. A directive like "Scan cruiser" appearing at the beginning of a mission in which the cruiser isn't discovered until halfway through just looks silly.
Hope that helps.