Strikes me as inappropriate for a government entity to declare bankruptcy.
Bankruptcy is a business process wherein a faulty market concept (bad business idea) is eliminated in a way that creditors get compensated.
Governments are not going to stop being governments and step aside in favor of "something else."
At least, not without lots of angry people with guns, tar, feathers and pitchforks. I don't think I've ever heard of a city dis-incorporating once it is already incorporated.
The best that Detroit should be allowed to do, is stop future expenditures. No pensions for new hires. Eliminate the programs that exceed the budget. Liquidate assets to offset insufficient income. They aren't looking to exit the business of "government." They're just looking for an excuse to stop paying people, get out of debt, then start the exact same damned thing over again with a clean ledger.
"Detroit" isn't going to go anywhere. The land will always be there. Some population will always be there. If Detroit loses so much population density that it can't pay for the pensions of all the folks it used to hire... it'll go into debt for the next 25 years to pay those off. And it won't offer pensions to new hires. And it will sell its art museum and paintings. And it will lean down its operating costs. Until the monkey is off its back.
The lifespan of a city is measured in millenia... not years. 30 years of indebtedness is regularly accepted by lay folks who want to buy a home. Detroit will exist for centuries to come. Paying off this 30 year income lapse is comparable in its lifespan to me not having ready cash to buy a new tire for my truck when I get a flat, and whipping out the credit card instead. I'll pay the tire off over the next month or two.
It might take Detroit 50 years to emerge from this debt.
But shrugging the debt elsewhere just increases the "privatize gain, subsidize loss" mentality that is sweeping the nation for the last decade or two.
All those pensioners would end up getting something from FedGov, which comes out of the whole country's pocket, and everything keeps on as it was. None of those politicians or city managers or bureaucrats will be held accountable for a solution to the problem, and the problem will keep happening since the "solution" is to distribute the debt wider and wider. Until the number of small debts is so numerous that it is insurmountable.
Synopsis: If there's no dis-incorporation, then no bankruptcy should be allowed. Let people decide if they even WANT to be part of "Detroit."