Interesting, with the low-density atmosphere of these "Puff Giants" as I am going to call them, are going to be very interesting to simulate. How do these form? How do these puff giants evolve? Are they the result of a Brown Dwarf burning out?

This seems awesome! Although, even though saving the earth is going to be hard and expensive, it's going to be a LOT more expensive to terraform/colonize a moon/planet, including our own!!!