1) Seamen generally aren't used on submarines. They weigh too much and do not provide enough boost to the crew to justify their weight. In subs, weight is everything.

2) Engineers will be able to provide massive amounts of overheat at high levels. They don't do a whole lot at low levels but eventually will be valuable. On a BB6 most people say have at least 4-5 engineers, and pack as many as you can on a sub.

3) Kaiser server population is smaller than Nebraska. Nebraska was formed by merging Iowa and Yamato (the two biggest servers by population) and Kaiser was formed by merging Bismarck (the smallest of the 3 original servers) and Nelson (the newest and by far the smallest server).

4) In a recent patch, maximum ship limits were reworked in GB1 and GB2 making GB1's able to hold more people, thus they are the preferred gametype now.