Long distance space travel is full of problems.
The gravitational issues on bones and muscles could be mitigated somewhat by rotation of the shop. This “inhabitable ring” could be where the crew spend most of their time. A HUGE PROBLEM will be radiation from both the sun & cosmic rays, etc. but also by the fact that space is not truly empty. It has some particle density from an estimate 1 H atom per cubic centimeter to much more. As a spaceship travels faster say gets toward some fraction of light speed. Those space particles will be hitting the ship at that speed plus whatever velocity they might have. The ship will effectively be like an “experimental target” in a particle accelerator. You can mitigate it to some extent with thicker hulls but then the hulls will become irradiated and be a problem. You can move the charged particles out of the way with electric fields but uncharged particles would still be a problem.
A big engineering challenge!
On a Mars trip, do the powers that be expect the astronauts to land, pop the hatch, and start exploring? When crews come back from the ISS, they are wobbly and need assistance to move around. Once on Mars, there will be no assistance. How long will they have to adjust to the Martian environment before they can head out the door?
Shop=ship. Stupid Surface!