You guys really should start thinking about a North Illinois and a South Illinois. Make two states out of it! Just make the border 10 miles beyond the suburbs of Chicago.
Actually your idea has been discussed before. Even though this article is from Huffington Post, it is an interesting read on the topic.
http://www.huffingtonpost.com/2011/12/09/illinois-chicago-split-pr_n_1140396.html
Back when my folks still lived in Illinois, it was commonly held that everyone outside of Cook County would like to find and cut the mooring lines so that it would fall off and sink into Lake Michigan.
...the punchline said that the tactic was doomed because sh** floats.
(Actually, it's MORE than hopeless. If the rest of the state went away, who would pay for all the "Needful Things" in ChiTown?)