>Firstly, there's no reason the trip can't be one-way, or at least, temporarily one-way.

This is the ultimate admission that it can't be done. Anyone sane would at least propose a free-return trajectory like Artemis 2. Even if you are crazy enough to sacrifice your astronauts on a one way trip, you would still need to practice a lot of free-return trajectories just to train your astronauts and test the hardware.