Build a fusion candle.

You have a large gas giant? Perfect, you have a world mover with its own reaction mass/power supply.

I assume this gas giant has a few largish moons? If not, move it around the system to capture some other suitable planet.

Forget the asteroids, they contribute nothing of value, at least concerning raw mass. (Wikipedia: "The total mass of the asteroid belt is approximately 4% that of the Moon.") Maybe use a quick sweep with your gas giant to clear it.

Once you have your mobile gas giant with one or more nice rocky satellites, move the assemblage in a cozy orbit and start to terraform the moons. If you did it just right, those icy asteroids you swiped earlier, or maybe a saturnian ring, can provide the water for your oceans.

The biggest hurdle is your time plan. I don't know how long the astroengineering will take, but 1000 years isn't even enough to build habitable biospheres from scratch.

You'll really want to start (while all the big moving goes on) by constructing closed ecologies to resettle your tribe, with mining and farming, which will extend the time left to you. No need to restrict yourself to an all-or-nothing / ship-or-planet choice.

Build a fusion candle.

You have a large gas giant? Perfect, you have a world mover with its own reaction mass/power supply.

I assume this gas giant has a few largish moons? If not, move it around the system to capture some other suitable planet.

Forget the asteroids, they contribute nothing of value, at least concerning raw mass. (Wikipedia: "The total mass of the asteroid belt is approximately 4% that of the Moon.") Maybe use a quick sweep with your gas giant to clear it.

Once you have your mobile gas giant with one or more nice rocky satellites, move the assemblage in a cozy orbit and start to terraform the moons. If you did it just right, those icy asteroids you swiped earlier, or maybe a saturnian ring, can provide the water for your oceans.

The biggest hurdle is your time plan. I don't know how long the astroengineering will take, but 1000 years isn't even enough to build habitable biospheres from scratch.

You'll really want to start (while all the big moving goes on) by constructing closed ecologies to resettle your tribe, with mining and farming, which will extend the time left to you. No need to restrict yourself to an all-or-nothing / ship-or-planet choice.

Build a fusion candle.

You have a large gas giant? Perfect, you have a world mover with its own reaction mass/power supply.

I assume this gas giant has a few largeish moons? If not, move it around the system to capture some other suitable planet.

Forget the asteroids, they contribute nothing of value, at least concerning raw mass. (wikipedia: "The total mass of the asteroid belt is approximately 4% that of the Moon.") Maybe use a quick sweep with your gas giant to clear it.

Once you have your mobile gas giant with one or more nice rocky satellites, move the assemblage in a cozy orbit and start to terraform the moons. If you did it just right, those icy asteroids you swiped earlier, or maybe a saturnian ring, can provide the water fror your oceans.

The biggest hurdle is your time plan. I don't know how long the astroengineering will take, but 1000 years isn't even enough to build habitable biospheres from scratch.

You'll really want to start (while all the big moving goes on) by constructing closed ecologies to resettle your tribe, with mining and farming, which will extend the time left to you. No need to restrict yourself to an all-or-nothing / ship-or-planet choice.

Build a fusion candle.

You have a large gas giant? Perfect, you have a world mover with its own reaction mass/power supply.

I assume this gas giant has a few largish moons? If not, move it around the system to capture some other suitable planet.

Forget the asteroids, they contribute nothing of value, at least concerning raw mass. (Wikipedia: "The total mass of the asteroid belt is approximately 4% that of the Moon.") Maybe use a quick sweep with your gas giant to clear it.

Once you have your mobile gas giant with one or more nice rocky satellites, move the assemblage in a cozy orbit and start to terraform the moons. If you did it just right, those icy asteroids you swiped earlier, or maybe a saturnian ring, can provide the water for your oceans.

The biggest hurdle is your time plan. I don't know how long the astroengineering will take, but 1000 years isn't even enough to build habitable biospheres from scratch.

You'll really want to start (while all the big moving goes on) by constructing closed ecologies to resettle your tribe, with mining and farming, which will extend the time left to you. No need to restrict yourself to an all-or-nothing / ship-or-planet choice.