>>What about a "Trader" class? He might not fit scoundrel or noble even though those would be the two closest!<<
Perhaps Traveller should have a Trader class, but within the Star Wars paradigm, the Noble class is intended to be more inclusive than its name would suggest. Rather than only representing 'nobility' (ie. the Princess Leia archetype), it can also represent any character who uses...
'...their intelligence and natural charisma to make their way in the galaxy. From true royalty to elected officials, military commanders to crime lords, traders, merchants, ambassadors, holovid stars, and influential corporate magnates...' (p42 SWRPG)
For gamemaster characters, there's also the Diplomat class, most of whom are 'minor functionaries or independent businessmen...local politicians, astute barristers, and canny merchants'. (p215)
Though I know little about Traveller, I'm very familiar with all the D20 games. I'll almost certainly buy T20 when it comes out, and if I like it, I'll eventually get around to buying older Traveller continuity/setting-related material. As far as T20 goes, remember that the classes of a D20 game should represent the archetypes that best define *that particular game and setting*. I mean, theoretically, you could have straight-outta-D&D Barbarians, Bards, and Druids (or Deadlands Gunslingers, Hucksters, and Braves)...on some backwater planets in the Traveller or Star Wars Universes -- but there's no reason to try to model them in the T20 or SW rulebooks, since they're not an archetype in either setting (though a GM could easily insert any D20 class in his home campaign). SW D20's classes are, rightly I believe, drawn directly from the archetypes of that setting (not the other way around). So, the Noble exists because of Leia, Fringer because of young Luke/Anakin, Scoundrel: Han/Lando, Jedi Guardian: Luke/Vader/Obi-Wan, Jedi Consular: Yoda/Palpatine, etc.). SW D20 isn't a D&D clone, nor even a generic sci-fi ideal. If T20 tries to closely model other D20 games' classes (SWD20 is obviously the closest match), then you'll end up with something entirely unsatisfying, like 'The Foundation', a lame D20 superhero game that essentially tries to present a superhero universe using only a few minor modifications to the D&D D20 game -- and includes such incongruous things as Wizards and Sorcerers. On the other hand, if you try to make Traveller too generic, you'll end up with Alternity (which was OK, but...er...generic). I suggest distilling Traveller archetypes which have persisted throughout Traveller's various rules incarnations (and the names of the classes should evoke those archetypes as well). The one nod to the D20 system Traveller should probably make, is that every D20 game thus far has had a skill-master class (D&D Rogue, SW Scoundrel, Deadlands Huckster), and a combat feat-master class (D&D Fighter, SW Soldier, Deadlands Gunslinger). Hopefully we'll end up with a *Traveller* D20 game, not a D&D- or Star Wars clone, nor a generic sci-fi game (though if Traveller's rules additions are good enough, then people will buy it for that use as well). Good luck!
Shane