Hi Atle! I'm late for the reply party, but I'll still give you my input. Make a proper seperation between loyalist locations and normal populace locations. What I mean by this is making like the grass well trimmed while the other is grown up, trash litters the streets for the regular people and while for the loyalists have the streets even sparkle and be well taken care of, with big parks, comfortable and new benches for people to sit in and well furnished apartments.
As for the normal people, have it go with overgrown grass, dying trees, crappy apartments and have mostly stalls/those kinda food vans instead of stores, which in turn for stores, there'll be like just 1 crappy bar or something like that.
For Overwatch, it would be cool to have this mixture of Combine aesthetic and a Geneva touch to it. They could have an outside yard for them to train, eat and play basketball, and for the interior just a super simple general area for them, armory and the sorts. That or maybe multiple small outposts that each serve their purpose. Like an armory, medbay, jail, so on.
CWU could just have either a factory or a huge warehouse and the CMU some sorta epic Mercy Hospital.
The rebel area I think its cool as it is.