This answer says:
We do not have a human-rated rocket which can send a sizable payload to Mars. The Falcon Heavy is certainly capable of sending a payload there, but the rocket would need to be human-rated, which basically means tested far more extensively than it has been now.
And that got me thinking - for a vehicle to launch from the surface of the Earth it needs to be pretty substantial. But you can avoid a lot of the requirements of the stresses of launch by becoming a payload (e.g. satellites wouldn't survive a launch if they weren't inside of a rocket. And if it were economical to build satellites that could be self-launching, they'd already exist, right?).
So would it be better to just build a ship in pieces and just send it up on a (couple) of Falcon Heavy Rocket(s)?