Create variations of blocks and thicken them in Galapagos


I have built a neighborhood in grasshopper, with certain density, and I want to use the galapagos as tool to thicken this density, but I’m having troubles in doing so.
In the neighborhood there are several buildings with different height, and its creat Heterogeneity in the area. I want to keep that, but I want to see if I can make it more croweded, by adding floor or 2 on some smaller buildings, or lower some higher buildings, and see what happens.

its image of some blocks in the area, with different heights.
I placed them in bounding box and subtracted the box in the buildings, Thinking that the galapagos will add the “missing” volume in the buildings.
at first I tried to thicken with X,Y, Z but the polygons kept to “clash” each other, so I just did extrude Z.The (3.2 MB)

It is obvious that it didn’t work.
it there any ideas how can I do something like it or its too complicated?

thank you all

evenatully, I sorted the buildings to 2 types: 4m and down, and 4m and up.
then I placed them in bounding boxes and measured thier volumes - made it the fitness.
then I took the buildings base curve, and gave them extrude. I had to place random component, so each building will extrude differentely. in the end I made some variations, but Its seems too randomaly and irrevlent to the idea.
any suggestions?com-optimize The (3.5 MB)