I was thinking about something... Those hard codded crew efficiency modifiers could be used in many ways. We only need imagination...
For example, what about players ability to "disable" his watch crew from any possible reason he can think of (leaving/entering port maybe, friendly convoy in sight) ?
This could be also applied for other sensors which can not be usually turned off (RWR, hydrophone ?)
Or even, "don't waste ammo" ability which will slow down the rate of fire but increase accuracy simulating careful aiming?
How about simulating the ending of Das Boot? An ability to send your entire crew to sleep in order to save the oxygen, with only few people still awake to finish up necessary repairs?
Really , the are lots of possibilities. We only need some imagination to utilize them realistically...