First forgive my terrible terrible graphic skills.  I'm trying to pitch the idea, and the picture just serves as a reference made of a lot of terrible copy-paste with MS Paint.

The suggestion is to add a window in the sailor display for all sailors that are tradeable that displays all information relevant to the history of the sailor.  A lot of effort is required currently by the individual player when purchasing or trading sailor crews, which means a lot of time and math when it comes to trying to calculate base growth and true ability/total crew.  Adding the window to sailors will take the guess work out of it by showing the base stats the sailor had when created, as well as promotion history showing the sailor advancement and the level that they underwent the promotion.  It is intended to show the level the sailor was promoted, not necessarily the level that the promotion was first available if they are delay classed.

Make this window available including in the in-game trade system, and players will no longer be required to keep a pad and paper nearby to calculate the truthfulness of another player before making a purchase or blindly accepting someone's sailor name that says something is base +12 as truth.