Hi,
Well, this is a 'design problem' .. There's no software in this world that does 'good design' for you.
Imagine the problem of placing 1 building on 1 square parcel. There's literally an infinite variation of results possible. Can any computer solve this problem well ? No. Especially not, since urban design's an n-dimensional problem.
CityEngine provides the tools that help you design faster, reduce the iteration times considerably, but it's not a blackbox that spits out a well-designed masterplan. 🙂
CityEngine is a 'procedural modeling application', so it's really fast at producing 3d models based in input shapes and attribution. What you ask is basically to wind up with the parcel / footprint shapes in the first place, which is the actual design process. Of course, you can write CGA code that produces such shapes / distributions, but the 'semantics of the design' you reach for must be encoded in CGA.
==> 'Some' things are faster/more efficiently designed by hand instead of writing the rules. It's all about balancing things..
(Sure, you can do these things in CE, I just want to state this honestly.)
Does this make the situation a bit clearer ?
Matt