There have been a number of proposals to fix what ails Detroit by importing hundreds of thousands of skilled immigrants to help re-build the city.
This idea will not work.
The 67% decline in the population of Detroit is the symptom, not the cause, of the decline in that city.
People have fled Detroit because it has been ruled by Democrats for over 60 years and has implemented a number of anti-business, high tax, anti-freedom proposals. The affluent and the middle class have the resources to relocate and they have done so in droves. They fled the policies of socialism and decline.
Importing new people to live under the same failed policies won't change anything.
Those people will remain mired in poverty and dependence along side the current crop of residents of the Democratic plantation.
If you want to save Detroit you need to change the policies, not the people.