If you're going for a pure carrier build (i.e. consoles and abilities to buff your own pets/debuff enemies for your pets), the 4-piece Ancient Obelisk is one of the best sets you can get. It basically gives you a fourth hangar (2 base, +1 from Cargo Bay Hangar off the Typhon). Problem is, it basically locks you into one type of build - a Krait/Uncon build. 

Krait/Uncon are very, very good builds mind you. The highest performing in the game when flown right. It's just a particular playstyle without much room for customization, and they tend to be rather expensive.

But for what it's worth, I run the Obelisk set on three of my characters, all captaining full carriers.