Looking good man! A few suggestions if I may.
Make sure that you can shoot through the fence you added in that interior spot - the one in the warehouse outside blocks bullets, which I have been meaning to fix. You might need to disable collision on the model and then put a tool brush of some sort over it. I don't think that is a very good spot for an obstacle though, people coming out of the warehousey area will get stuck, but it might funnel them through a window instead. Playtest it
That scaffold is nice, but it might cause some collision issues if you stunt about near it. Make sure the collision on any structures is as blocky as possible. A way to do that is instead of having a single crossbeam, make a whole section of wall, or even a handrail with a half wall underneath it. I worry that anything less than 16 units across will cause issues in the heat of battle. You can keep a high level of geometrical detail while having simple collisions if you create more dense details and put a tool brush over the whole thing, as opposed to thinner gaps and collide-able pieces (if that makes sense).
I love the garbage chute. There is already a stock dumpster model though, the same one that is on top of the construction site on streets.
With the wooden framework in the construction area, you'll get more detail out of it if you add a bit of higgle and piggle. For instance, the studs (the short horizontal bits of wood) are usually offset so the builder can get a tool in the end, for punching in nails, like in this image
. Also some cables are nice. I've been meaning to make some cable models for all our construction site areas...
Finally, for the underground area with the shipping containers and the boxes, that whole area never really made sense. I was going to make it a workshop area with cars on hoists and such, but I never got around to it. In any case, change the textures and boxes up a bit. We have a whole bunch of crate models (search in the model browser for 'wpncrate' or some derivative) that could spice that area up if you plan on leaving it as a warehouse.
I'm liking your touch up, it's great to see someone doing something. Progress is slow atm.