This gives you so much more tactical flexibility than most games. Missions come in a wide variety of types and objectives. There are search and destroy, attack an objective, defend an objective or convoy, capture structures, vehicles or even barges, and many others. Frequently, once you get past the first set of missions, the missions are multi-part. For example, in one mission you have to escort a convoy to an enemy base, take out the base defenses, wait while they scour the base for supplies and then guard them on their way out of the area.
Salvage is semi-dynamic.
Some salvage is scripted, but anytime you destroy a mech there is a percentage chance that you will get that mech as salvage. One of the best things about MW4 is that boating i.e., the practice of loading up a mech with huge numbers of one weapon to take advantage of that weapon's superiority, is dead. You simply can't boat anymore. You can't boat because of the hardpoint system that has been instituted in the Mechlab. A Vulture, on the other hand, has four missile hard points in the right and left torsos, two omni hardpoints in the center torso and two beam hardpoints on each arm.