Adventure 5 Trillion Credit Squadron and the colonial economic model in World Tamer's Handbook (and don't get me wrong, those were good and potentially useful for the subject), but in the fourth edition, Marc Miller's Traveller (also called T4 for short), the supplement Pocket Empires came out.
Oh, this was a joy for me to see. Finally, the game would support campaigns inspired by Dune and other sources involving high-level politics and intrigue. There were rules covering everything from the economic development of worlds to incorporating new worlds into your pocket empire to setting up and finalizing a marriage between members of your noble family and another one. Assassination attempts, espionage, politics on the floor of the Senate, all of these things were covered in the high-level game here.
There were some weaknesses, of course. The basic game had a development turn a full year in length, which could lead to pretty severe discontinuities between the Pocket Empires layer and the roleplaying layer. The rules for voting factions in politics were a little rudimentary, but still serviceable. The military forces abstractions were perhaps a bit too abstract (although this was at least partly remedied with the addition of Imperial Squadrons, which was a major revision and update to T4 standards of Trillion Credit Squadron). The handling of corporations avoided many of the things that give that aspect of play its distinct flavor, with no insider trading, no boardroom politics, no shares changing hands, only what amounts to an abstracted hostile takeover and a few other simple tactics.
Some of the elements of the noble life have been handled over the years. I mentioned a number of resources in the last installment of "Alternate Traveller Campaign Frames", and at least one more has appeared since then in the form of an article titled "The Influence Game", posted over at Wayhaven Traveller, which could be used to fix the lackluster politics rules in Pocket Empires.
A lot of these different layers include the idea of a turn length of a week to a month. It shouldn't be hard to incorporate that into the main Pocket Empires sequence. That would fit everything more tightly to the roleplaying layer of the campaign, which effectively has a "turn length" of one week, since that's how often Patron and Rumor checks are made, how long a Jump takes, and so on.
All of this is important to me, as I am (slowly) working to convert Pocket Empires to MegaTraveller standards. I think that edition is the easiest to convert to any of the various other editions out there, so that it could be easily used with CT, CE, MgT, T5, or whatever. I intend to flesh out the corporate section and the politics especially, but also spend some more time on the military elements. Integrating it more completely with the roleplaying is my priority, of course. Setting out a specific method of generating the Noble House and its starting assets will be important too, as will working out ways to incorporate the players into the House.