The early levels go by so fast, there's no reason to late-class a gunship BO. Just roll
yourself some throwaway gunners and use them to level your 2nd BO to where you want him.
Or, better still, roll yourself some decent gunners and plan on classing them the
anti-aircraft route, because you'll need those on your BB anyway, and use them to level
your 2nd BO.

--Helms

BOs can board only the ships they are chosen to command. You may board an unclassed
neutral sailor and grind it and then turn it into a BO, but you'll be missing some ability
in the end.

Briefly: NO. Plan ahead.