Raise the costs of sailor training (raising ranks) and
tune it so that they cannot be automatically trained
but require sailing (read experience) to get more ranks
(of course, cannoneers don't learn by sailing but by firing
cannons and liftmages with flying).

Make specialists and training costs higher
Limit ranks to some certain amount (increase from 4).
Remove trainers automatic rank increase, but make em lower the
"experience cost" of sailor for the next rank or make them
help gain crews experience with higher rate.

Not to mention getting to rank 6 sailor could require quite a much
of sailing experience and I would imagine its not too cheap either.

look who has a ship allready

Well if its about that, reset all the crews to rank1 so everyone will start
from the same line?
and its not prolly my fault i build it in advance. but there are some thing,
especially in this trainer systems that are bothering me (idle/robot enough to
get best crew)