Oh, interesting!

Shouldn't it be possible to then feed that into a fitness function and randomly "evolve" the "perfect" distribution, or is that silly?

Totally possible. Though getting data out of WebGL can be hairy. And actually getting on the rooftops of the ideal buildings is a whole nother story.

Make ease of access (and how much it's wanted there, and so on) part of the fitness function, too :)

And future configurations could also take into account how many things you'd have to move, or whatnot (I have no idea about what you're doing, I just imagine that's not something you do once and never change, right?).