Under current law, there is absolutely zero legal option to reduce Illinois pension benefits by even a penny, so Illinois must attempt to beat the pension liabilities out of its tax base. As this necessary action causes the comparative advantages to living and doing business in a neighboring state vs. Illinois to become more and more apparent, exodus from the state accelerates, which renders further attempts to increase taxes more and more harmful to the end objective of having enough revenue to pay the debt service. At some point, they can't pay the pension debt by leaving tax rates where they are, and they can't pay the pension debt by raising taxes. This becomes a death spiral for any non-monetary sovereign government or other entity.
And once it's come to that, then at that point, no matter what, there has to be a change to federal law in order to deal with a state that is insolvent. There is literally no legal way to deal with this other than to pass a new law that flies in the face of previous practice. You want the feds to bail out the state's self-sabotaged pension with fiat money? That requires a brand new law. You want the state to be able to declare official bankruptcy? That requires a new law. Want to cut the state into fourths and merge it with its neighbors? That would require one hell of a new law allowing that. There's nothing that can possibly be done to deal with this other than a brand new law being passed.
And when those measures are being considered by Congress, all I can do is pray to the heavens that people in this country take notice and decide to start giving a ****. Because historically when it comes to pensions, most people fail to even remotely care, and most of those who have decided to care still don't bother to understand the full nature of the problem.