I think they should look to 18f as an example of how to bring private sector folks in for a time. Just like a startup can't compete with Google/Amazon/etc on benefits and salary, so has to compete on different dimensions (mission, ability to grow, equity, etc), the government and the NSA have their own strengths.

Salary is not one.

I am no expert on the NSA, but I imagine some of their strengths are:

Mission

Scale

Advanced tech

Real world impact