Raise roof / add a dormer ON TOP of current dormer?

[Jacob D.]

I'm looking for opinions / guidance on whether or not this is possible - from a city regulations stand point:

The second floor of a 2 family has an attic space with stair access from the 2nd floor apartment. The attic space is really open and has 8 feet high ceilings (the roof).  The problem is, the pitch of the roof prevents the entire space from being livable. I want to do one of two things:

1. Change the pitch of the entire roof, making the attic space useable (which adds ~800 sqft)
2. Add dormers to the ATTIC (not the second floor which already has dormers)

For 2. I'm guessing to add dormers to the attic, it will have to be built ON TOP of the other dormer that exists on the second floor. The below pictures are from both sides of the roof:

Any idea about how much it would cost to raise the roof or add more doormers for the attic space?

I'm not trying to make a new apartment in the attic, I'm simply trying to add a bedroom or two in the attic (although it would be even better to add an apartment).