For talking heads/opinion you have, I would say, two choices:

    - Retired people with historic experience.  The longer since they were actively involved in the sector, the less useful they will be of course.  There is also going to be something of a demographics bias here.
    - Currently employed people, and given their primary skillset is "Defense industry expertise" I'm going to posit that they always have a commercial role in the defense industry.  Maybe there's some subset with a non-commercial role or a purely political role... but both of those have their own implications too