For character classes, something to keep in mind: in most class-oriented games the character's class represents an archetypal definition of 'what the character does,' be it fight, sneak around, cast spells, or whatever. Traveller's careers/professions don't really work that way, and really reflect 'what job this character used to have before deciding to become an adventurer' (traditionally all Trav characters have retired (or been booted) from their 'career' before play ever begins; though later editions have blurred this rule somewhat).
Theoretically I suppose the most accurate way to handle this conceptual difference would be to have 2 distinct sets of Classes: the 'career' classes (Army, Marine, Navy, Scout, Merchant, etc.) primarily for NPCs and Prior Experience in char-gen, and the 'adventuring' classes, which would be things like Mercenary, Free Trader, Rogue, Traveller, etc (ie- more function-based, and reflective of the types of things Traveller PCs actually do in-game). The extra level of complexity and almost-certain confusion this would add to the system (as well as an at-least-implicit incompatibility with previous editions) may mean this isn't the 'best' method, but I do think some acknowledgment should be made of the fact that a T^20 PC with the Marine character class (for example) is almost certainly not still enlisted in the Imperial Marine Corps.
Theoretically I suppose the most accurate way to handle this conceptual difference would be to have 2 distinct sets of Classes: the 'career' classes (Army, Marine, Navy, Scout, Merchant, etc.) primarily for NPCs and Prior Experience in char-gen, and the 'adventuring' classes, which would be things like Mercenary, Free Trader, Rogue, Traveller, etc (ie- more function-based, and reflective of the types of things Traveller PCs actually do in-game). The extra level of complexity and almost-certain confusion this would add to the system (as well as an at-least-implicit incompatibility with previous editions) may mean this isn't the 'best' method, but I do think some acknowledgment should be made of the fact that a T^20 PC with the Marine character class (for example) is almost certainly not still enlisted in the Imperial Marine Corps.
