I don't think it's just a rules issue. What about a bestiary? Yes, there are the Aliens of Charted Space books, but did you remember to cut out all the races in JTAS? From other Sector specific adventures? What about culling all those vehicles and equipment spread over a hundred books and articles?
My two biggest issues w/ Mongoose's approach to Traveller are:
1) With the obvious exceptions of Travellermap and the Traveller Wiki, there is no online, easily accessible source for any of the actual rule materials (vis-a-vis d20PFSRD...) in a way built for players & Refs trying to quickly find specific rule explanations...which of the 50 most recent books did I read that rule in???)
2) even worse, all their books and materials read like they are written for players who want to hear a story, not for Refs who want to run a game....meaning rather than giving Referees the critical information in clean, simple, efficient formats and tables, Mongoose (even in campaign books made for Referees) spread all the info into a narrative form which means I need to spend weeks culling out the relevant info into digestible, effective, playable notes. What is the benefit of having a publisher so focused on RPGs if they are doing very little to actually make the Referee's job any easier?