Detroit is actually reinventing its economy right now as we speak and is moving towards rivaling Chicago as America's premier logistic hub with some of their plans. Those are incredible ambitions and I hope they go through for Detroit (so far seem to be approved).
Detroit also have a few natural advantages it can use, it is the largest border city in the USA and also handles the most trade between the USA and any of its given border country counterparts, it needs to start improving its fixation on that and be more competitive.
Detroit is also on the worlds largest fresh water source, not that it means anything now, but its always a very handy asset and a permanent one to have for any future insight that may ready itself.
I think Detroit can reinvent itself but I do think it will take time, a few years at least and I hope after economically reinventing itself it also fixes up its inner city areas. That would be great too. And it's economy is more diverse now than most will realize, however it wasn't very much diverse when it started to backfire decades ago. Detroit just began diversifying too late in the game, but can hopefully sustain it.
The Michigan business climate sucks though, they pay some of the heaviest taxes in the country and the incentives while nice aren't ever lasting. Detroit needs to figure ways to work around that and still attract more commerce. Detroit is more educated than Miami as a metro by far and away, but its city lags, and it needs to enforce education more strictly and work on improving that.
Miami, it has to educate its populace first and foremost. And get rid of these low wage and petty jobs that aren't beneficial.
Las Vegas, this is a tough one but they are going to have to start diversifying themselves. They have the potential to do so.