Why not do what every company does? Have a recruiter go out and seek the best candidates.
The government could let a contract to a recruiting company or companies. When a job vacancy becomes available, the recruiter can search for the best candidates. This is very effective in the private sector. It is fast and cost effective.
This would eliminate a lot of problems. For example, if there is an internal candidate, they could than have to justify why this person is the best. I believe in promoting from within. This would eliminate the charade of having fodder candidates. That is having a preselected candidate that you will hire and having other candidates apply (who are rejected) so we can say we have picked the best candidate.