I get your point, but I think what your describing isn't particularly meaningful. By definition, nearly 50% of any population is categorically an undesirable surplus.
Yes, you could argue that. But a _nation_ could improve its proportions by restricting immigration to a subset of the _global_ population.
To a certain extent, this principle is applied today. But I imagine it could be scaled up to something akin to highly selective university admissions process (e.g. interviews, standardized testing, resume critique, references). If a country starts with sufficient desirability, this could result in a positive feedback loop -- an increasingly competent and productive society.
I agree with you there. Unfortunately, the greatest motivation to bring in someone outside the country is rarely for their exceptionalism, its usual about making/saving money. And at most institutions, its far more cost effecting to get individuals who are just sufficient and will accept a substantially lower compensation than their domestic peers. The individuals who are exceptional have loads of options/opportunities in their own homeland.
To a certain extent, this principle is applied today. But I imagine it could be scaled up to something akin to highly selective university admissions process (e.g. interviews, standardized testing, resume critique, references). If a country starts with sufficient desirability, this could result in a positive feedback loop -- an increasingly competent and productive society.