I think the premise of copying the mind to a machine is the right direction and you can do it like that, but it would be faster to try to make the initial "Seed" trip using the lowest mass ship possible and not carry any human because if you have mind to machine tech you can also beam humans at the speed of light, so you goal is to setup a receiving station and beam humans... because basically the only thing that travels through space fast enough is electromagnetic radiation like light and radio waves. Everything else has to either be flung with impossible supernova level forces or accelerated with super energy dense fuel that doesn't exist. We need something that can accelerate over time and not be limited by fuel or size so much, tiny probes accelerated by lasers fit the bill better than anything else I can imagine using known physics.

So instead of that I would say you just send swarms of self assembling robots at a fraction of light speed using ground or space based laser propulsion. You keep the ships ultra small so they can get up to a fraction of lightspeed and hopefully slow down using gravity and surviving the landing. Slowing down is one of the harder parts.

Traveling at fractional light speed might be dangerous due to random debris in space at those speeds so you don't know if all your probes will survive and it doesn't really matter since they have minimal value.

The robots build a receiving station and basic outpost on the remote world and then you can send humans at the speed of light as data instead of fighting the mass acceleration and huge amounts of time problem.

The important part here is that this method allows you to travel at lightspeed without breaking or pushing the laws of physics to the max once you establish your outpost/receiving station. There is no impossible amount of energy needed, the hard parts are copying the brain to electronic format, making some half smart self assembling robots and slowing down the microprobe from fractional light speed to landing speeding while being at max distance from the laser propulsion source AND doing all that with the lowest possible mass of course so you can actually get to fractional lightspeed.

Once you have your outpost setup you can send humans to control machine or clone the human and perhaps transfer there intelligence into the clone as far as seed biological life on a suitable planet.

However... once you have the human brain copied and working in a computer it begs a new question. Why spend all the effort looking for just Earth like planet when a human mind in a machine can live almost anywhere, including just inside a giant computer using ultra low resources.

Once you can copy a mind and render it in a computer you have a whole new way of sustainable existence and long term survival that biological lifeforms can't really compete with. Sure we will be trying to find Earth like planets, but it might turn out that we can build robots that build robots so much longer before we can travel to another solar system that you basically have planet building technology in your own solar system before you can actually find and get to another Earth like planet. Who knows how close the nearest Earth like planet really is, it could be hundreds or thousands of light years away. If so we will be building planets before we ever get there because the most we are likely to go is maybe 1/4 lightspeed and that's mostly just with the tiniest probes possible.

As far as carrying fuel and accelerating a larger ship. I think it's fundamentally not possible for anything but the shortest trips and that kind of slows down the process exponentially AND really getting probes to the would be target planet is a lot more important because you really need good data on it before you commit.

Sooo for now we need ground based microprobes that we can accelerate to 1/10-1/4 the speed of light because that technology might be something we can do soon AND we need those probes going out to target locations ASAP since that will take most of the time and in the 50-100 years it takes to get a probe to another planet we can figure out self assembling robots and mind to machine transfers.

I think that's actually a lot more practical than giant ships with ridiculous amounts of mass/fuel and you eventually can transfer humans at light speed between locations. You can "spider web" out through the universe a lot faster using that kind of low mass max reasonable speed approach. You're not investing huge amount of effort into a ship that will be gone for decades or hundreds to thousands of years and you really need to send probes first anyway so you'd be waiting for those to get there also.. why not just send probes than can assemble receiving stations and send humans like that.