The US already has an investment visa....the EB-5.

The problem with the current system is that its pretty opaque on how to conform to its rules. You need to invest in "new enterprises that hire 10 or more employees and invest over $800K in specific areas of the country"

All this becomes a headache of how to you monitor & measure all these things.

So really all Trump is doing is "streamlining" the current process (and raising the price).

In the early 2000s I remember reading an article that posited this idea and taking even one step further: The sale of citizenship could also be financed. So a new immigrant arrives, and like buying a house, must put down 10-20% and then needs to pay off the balance over 20 years.