Game: What game are you currently playing??

[Animeniax]

Yeah, defending and attacking isn't the same thing as objective-based assault type play. And I don't mean, hold the next point for 1 minute so it automatically proceeds to the next stage.

I mean, "You must use an Engineer class to rig the explosives," "Steal the plans before you blow the generators," "Cut the fence and escape down the sewers," or "Defend the tank so it can destroy the gates."

It's essentially "objective based" assault gameplay. Your first objective is to control the cannon points to damage the carriers. Then your objective is to destroy the enemy carrier or defend your carrier. Not quite as refined in scope as what you listed, but it's enough. I think the assignments force you to use certain classes and skills, so the gameplay doesn't need to. Though I would also like a game mode in BF like what you are suggesting.

[Ryllharu]

Not quite as refined in scope as what you listed, but it's enough.

No...it's really not. ET has optional objectives that make the next stages easier, objectives that either team can accomplish, and defensive build up.