Promoting from within is critical if you are attempting to maintain positive aspects of internal culture. It does cause slower responses to external cultural shifts; however, most people are not looking for the same thing in BSA that they are in other non-profits.
In my opinion, we want promotion from within, and every paid Scouter should have the strongest Scouting background possible. The volunteer positions can absorb the people with weaker or no Scouting background.
I was at UPS for 15 years, in management meetings I would always bark out, "When are we buying our company back?" because we lost a huge part of our corporate culture when we went public, and subsequently started hiring management from the outside. We went from work hard, play hard, take care of our people, to work hard, no playing, and squeeze the employees as hard as you can. Trust me, bringing in outsiders to fill critical executive positions will in a few short years obliterate the culture of BSA just like it has obliterated other non-profits and for profit companies.