Aye I agree with both the legions and the Cole/Bunch series. Likewise Cyberpunk genres etc.
But (and I'm nae sure here...) I was wondering if that they couldn't be covered under the Traveller section?
They might need an additional specific book to cover each one (or more), but I've a (for a want of a better word) feeling that might be a better approach rather than a stand-alone. It builds upon a (soon to be released) RPG and may allow for a greater exposure than just Game A or Game B.
From the previews given out already (Check out some of the alternate drives for spacecraft), Mongoose seems pretty open to additional ideas / thoughts about the "Space Opera" genre.
Take Care
E. Herdan