Put human bodies into suspended animation caskets (SACs)
This will be the most sustainable option because you do not need a lot of materials to run actual space. Living spaces must at all times be:
* sanitized
* monitored
* air-conditioned
* pressurized
* lighted
* gravitated
These requirements are just for designing a general livable space. Specialized living spaces like bathrooms, bunkbeds, kitchens, living rooms, cockpits, laboratories, viewing windows, etc., require a lot more conditions, meaning a lot more resources.
BUT if you just put everyone to sleep, then you just need highly sophisticated bunk beds that also function as dining rooms, comfort rooms, and all sorts of utility rooms. Your only problem will then be all about running a place where interaction is necessary and/or encouraged, i.e. cockpits, laboratories, and living rooms. 548
My solution is just to
Put human minds in full-immersion virtual realities (FIVRs)
Everything in an FIVR is limited only by what computational power your ship can allot for such simulations. The only thing you need to ensure is the hierarchy of command within the ship, the accuracy of your simulation compared to real-world physics, and the correlation of the simulation with the control processes of the ship.
Basically, you need to provide an interface for the simulation and the real world such that if the captain in the simulation decides to crank a simulated lever to steer the ship leftward, the ship will steer leftward based on the value of the cranked lever.
It would be like controlling the ship itself from within the simulation.
This simulation-reality correlation can be extended to all the other functions of the ship like
* running the simulation
* regenerating food sources
* administering intravenous nutrition
* navigating through space
Summarizing: The freedom and safety you desire can be efficiently provided by virtual spaces. You can place a sophisticated, self-sustained, single-size bed anywhere on your ship. You only need that bed to be able to read and carry out the thoughts of the person on it. Maybe just add propulsion and the bed itself can become the ship, or link several of these beds together and equip them job-specific extra utility functions.
TL;DR: By making the ship, the humans, and the interfaces between the two to be as integrated as possible, you do not need to know specifically where inside the ship should you put your humans. 500