Sorry, I didn't see this note until the thread was closed. I am disappointed that they closed it. I had a potential solution to the city collision problem.
I know they've stopped their ears now, but this was my idea:
When a world gets scheduled for destruction, everyone gets an invite to the new "smash up" world. If they accept, they go to a screen listing all of their cities with check boxes. The player would select all of the cities that he/she would like to keep. Next, the player gets a screen listing each city that is being kept, along with a new ocean number listed next to it. There would also be a randomize button. You can keep clicking the randomize button until you have something sort of resembling the ocean spread you would like. (Randomizing is much more atom-smash style anyways, and is computationally CHEAP.) Any cities that the player did not want to bring over get REFUNDED as free city slots (this is also computationally cheap).
Drop world wonders entirely. The mix up of city placements, rubbing shoulders with new players, along with a pocket full of city slots to spend on strategic moves would be really exciting imho. Bringing over the city slots is key. Anything that would not bring over city slots (like hero worlds) does not hold my interest.