I have an idea right off the top, but haven't got the time to reply in depth with sketch and such. I don't know if you're planning to play speedball or anything on it or if there should be any symmetry but here goes a quickie.
Put a big half-building along one edge, sort of like a long thin building and space out an even number of big, medium and small buildings (one of each?) to form to halves. with bigger road between (leading up to the half-building). This should give flexibility. you can play a lot of scenarios and game types.
Now I'm late.