Qualifications don't matter a bat in the control room. As long as you have officers -- any officers, qualified or not -- you will maneuver as if you had Uncle Karl's personal staff on board. You will dive, surface, turn, put topside watches, etc. as quickly as if you had an elite crew.
Do some throwaway careers out in the harbor... or go out to the North Sea and play with neutrals. You will find you could load out with rank n00bs or an experienced crew and your boat will handle the same.
Qualifications in the game count here, and only here:
- Dedicated repair POs and officers.
- Your sonarmen and watch officers for their acuity, though yours will always be better.
- Your torpedomen, for loading faster.
- Some machinists
Don't bother with:
- Helmsmen, ever
- Medics... lots of threads, but generally say it is of low value
- Officers as radiomen .. useless.