Sounds like a good plan.
I was gonna say to have it be luhmans rather than tau ceti, but luhmans sensors cover the Galapagoean JP, right? If so then we'd know immediately if a hostile fleet arrived that way and can send help from Earth so in that case a fleet in Luhman probably isn't needed. - Each system with a colony - and Luhman 16 has Claymore - will get a small squadron of Pirate Chasers anyway, for Trade Protection. The Pirate Chasers are only 2,000 tons apiece. Even a combined squadron of seven of them is cheaper and easier to maintain than a single AWACS or Carrier (25,000 tons).
Perhaps a squadron down in some of the barren systems? Or is it less likely somebody comes from there? - Except for knocking out the odd unmanned listening post, there isn't much DAMAGE that opponents can do to us there. Not until we expand past the Dead Suns waste. Or start mining the comets there.
But yeah, as we spread our we probably should have smaller squadrons here and rheee, and not just at the outer limits of our empire. But for now, the outer limits probably will do.
Will the pirate chasers be based out of that Base too? - I'm planning to base Pirate Chasers at DSPs, and Fleet elements at colony planets.
Could a colony atoll be built using lots of life support? - It says N/A. The gravity is too high.
I don't think we should split humanity in two. That's just a recipe for disaster. - Possibly so,