I think it would be reasonable to claim that the larger the proportion of smart people in your population, the better. If that's true, than any number of below average intelligence people would be a surplus.
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.
That is simply not true. Most countries do not have the demand, willpower or money to sustain, say, a world-class research institution.