Good improvment over the last sketch!
Railings are a little problematic. They usually look good and add realism to the scene but they also have a tendency to annoy wallwalkers and jetpack users if they are built in the middle of an area and buildables built on top will look severly out of place. I'd be interested in a new railing design that gets rid of these problems, maybe something with a solid, partly windowed wall and a small flat surface on the top.
The machines on the platform could shield off a default human base in front of the windows. I like that. The bridges are too thin for big aliens (especially since they have railings). If this room is going to be the human base, I wouldn't have three different entries on the upper level alone, so I don't think the forking bridges are necessary anyway. I'd rather build a single wider bridge that goes in a quarter circle or something like that. But again, the default bases can't be designed on paper alone, their layouts will most likely change a lot during development and testing.