Starting at what level? I joined a campaign at level 8. I have seen some deaths, you probably can increase battle sizes by 50% as the scenario is written for 4 characters.
Another suggestion on crew, list a minimum full crew and a skeleton crew. If you are below the minimum crew, you are at disadvantage. If you are below the skeleton crew you have severe problems.
I would allow the ship to do one thing at a time while under crewed but not fight effectively, I mean...