I hope there are possibilities to switch the carreer path at some point, afaik in the german navy it was rather common to serve as officer on a U-Boot on the trainingpath to the commando over a surfacevessel.
Maybe larger ships even need a multicrew to use them. I guess you surely are able to man a single gun but in battles the better places are the bridge and the batterycommandoposts (don't know how the correct english term is) of the different weapongroups.3) You mentioned having human players take over airplanes and be given direction during a battle -- are humans going to cooperate on larger ships? I've found that in some cases, AI gunners are better, but I think a heavy cruiser manned by human gunners may be a lot more deadly...


