The thing that matters most about Hivers is their motivations and manipulations. Those are detailed pretty well in the GURPS book. The character generation types of stuff from classic are compatible enough with Mongoose that they cover that. I think at the price of the Far Future CDs, there's not much to add that's urgent enough to put them high on the Mongoose publishing pipeline.
As for a compendium of races of the Imperium, that would be one really fat book, and adding the whole of Traveller charted space would be even bigger. I have four thick Far Future reprints of classic books, and I think about six GURPS books, and they're hardly comprehensive; I think there was an alien race article in just about every print JTAS too.
There are not that many races found through large spans of charted space. They're important enough to be worth their own books, or half-books as with existing materials. Regional races probably make the most publishing sense as sections of sector books.