This is how you make Metro a 100 times better.
First section needs to be spread out a little more. Not by much, just enough room so the boxes are not right on top of each other. Once that business is done and the entry to the tunnels are opened, there should be a way to stay above ground and fight through the city to get to the boxes via an entrance that was not blown to hell. Then we could have one firefight on top of another firefight. One being the chokepoint tunnels and the other being an urban combat zone.
For the final section, the buildings should be opened up some more so there are more places inside them to hide and fight. The A box should be on like the fourth floor of one of the building in a large open room, like a hotel lobby. There should be 3 or 4 entrances to this room. The B box should be in that mall or airport terminal or whatever that building in the far back is. The box should be in the center of that room under the escalators with at least a second floor for defense. The street before you get to that building should just be removed so as not to be too much room between the two objectives.