1. A concerted and aggressive effort to rid the city of gangs. This might require unusual measures, including the involvement of the National Guard and/or military.
2. Substantially lowering the tax burden on businesses/corporations that could locate there. This could include a ‘tax-free’ incentive period for entrepreneurs and start ups.
3. Measures to counter the entrenched Chicago cronyism, and political corruption.
4. Make Chicago, and Illinois ‘right to work’, and counter the influence of corrupt labor unions.
5. Revitalize as much of the South Side as possible. For example, there is a large swath of lakefront property where US Steel Southworks used to be. This is prime real estate, and if developed properly could be a nidus of growth for the South Side that would grow beyond it's boundaries. This would require, of course, efforts to make these areas safer. Given that the University of Chicago is down there, it could also be targeted for biotech development and other types of tech - kind of like the Research Triangle in North Carolina. This kind of growth could be linked to increased educational initiatives and programs in the local community.
This is just a start. That said, it won't happen, because Illinois politics is corrupt and the Democrats and labor unions are entrenched.
Chicago could be saved even more simply. Eliminate welfare in Chicago. Force anybody who wants welfare to move elsewhere. If the only people in Chicago were those who worked for a living, Chicago would be solvent.