What you could do is using SH3 mission editor open the 'Campaign_LND.mis' file and look for the air bases, zoom in and select the base then right-click/properties, you will see entry for CrewRating, change this & Save!
You could also open with notepad & do a search fo airbases.
Hope this helps.
Cheers.
EDIT: These changes will not work until a new patrol is started & not sure but may need to start a whole new campaign!