During a campaign game you can modify the ships assigned and crew quality by the edit command for the file aos0000x.cpg x campaign 1 2 3 4 5 etc.....

Ships are listed by line number in the main.oob file this is listing 1 in the columns format of 00000x.cpg. Just goto main.oob and select the ship you want

The second to last series of numbers in the column is crew rating:

0=a(best)
1=b
2=c
3=d
4=e