A built-in self-destruct. Also, I think you should move the whole city down to the bedrock(wall) to kill some of the lag. Perhaps a power plant too? If you want one, I can make you one :)
It's better if you have your own bomb, but I DO have an idea to do that... I know how to make a small power plant, I know just the build to put it over. See, the sand is being replaced by basements and such. The refinery/cnct plant/basements/bunker would not work if I did that.