I am not a big fan of cs_assault due to it's unbalanced gameplay. But I really like your changes and enhancements.
Maybe some of the air shafts are not needed, as I think there are already kinda too much possibilities (think about each needed or not and how it changes gameplay - coz too much can make it confusing and kinda annoying). Nevertheless I would add another major entrance to the hostage room, you have a great backyard already, add another big door/big window/open balcony. I would also remove most of the explosive barrels.
And it needs fps optimization. Some detail missing for example in the new part near ct-spawn. Radar/overview missing as well.
But overall a great map already (creative ideas, good lightning, great sounds, great detail, ...)! Not too much to finish actually.
Please give it a final touch to make the time so far not wasted. You show a good hand for it!