Not being located in Chicago, these following are just assumptions of issues that could be interesting to address for residents of Chicago.
Basically, there would be four areas that possibly could need some substantial funding:
1) transit (CTA, Metra and PACE), f.e. for new subway cars with a contemporary design replacing old ones, for expansion of the Red Line to 130th, for a more efficient and expanded bus service, service improvements on Metra like WiFi trains and more frequent service during the midday, more reliable winter service through investments f.e. replacing some of those decades-old track switches that froze, possibly new Metra DMUs / EMUs with contemporary design to entice more ridership
2) inter-city rail (Amtrak), f.e. funding for new equipment and improvement of all the corridors going out of Chicago in all directions, like the higher-speed rail to St. Louis, the higher-speed rail towards Michigan and a second daily train towards Minneapolis/St.Paul
3) high-speed rail, working towards the approval of funding to start the planning and engeneering process for a midwest high speed rail network like shown in the study of the University of Illinois / IL DOT last October, that will connect places inside of the Chicago area with each other as well as connect Chicago with other cities in Illinois and neighboring states, and even be profitable once it is running like shown in the study
4) more funding for CREATE, a public-private partnership already very successful in the past with relieving rail bottlenecks around Chicago, still now the program needs more funding
Those might be some things to mention, but only in case whatever is mentioned actually is something a resident of Chicago would like to support.