The defenses are not actually as severe as they could be!
You should consider preparing an invasion of the sanctuary. The automated defenses (at least in my case) has some advanced shields and weaponry which will pull you 50 years ahead in terms of energy, armour and shields technology.
Meanwhile it's also 4x25 tile ring world, which essentially function as Gaia worlds. I've used it to create fill out 4/5 core planets (and with Asimov, they'll take just one slot!). It's quite amazing to have 4 25 tile worlds to fill out your energy quota in mid-late game!
If you're into having a multi-species empire, making migration agreements with empires that have agreeable ethoses also mean that the world will be instantly swarmed with citizens of many races.