I like your idea of replacing nobles with political appointees, personally in charge of around a third of their tax collection, with another third going to the Imperial Navy and the final third going up the chain of command (presumably with the count, duke, archduke, and emperor each taking a cut, though how this final third gets spent is unstated). However, this necessitates the question of why we should continue to call them nobles. It seems more apt that they should be called governors or perhaps viceroys. Historically, and correct me if I'm wrong, nobles such as barons, counts, dukes, and such were powers in and of themselves, local strongmen who exercised direct authority over their populations. It seems to me that if we are to assume that nobles are devoid of the very characteristics which have historically defined the nobility, then maybe we should find them another name. I dunno. Every Traveller GM has to address these sorts of questions in their own campaign. As for myself, I do like this idea you've presented, but I'd be curious to see it fleshed out in greater detail. Have you ever produced any sort of write-up that goes further into the nuts and bolts?