First we'd need some FSD-related handwavium that would allow for the FSD bubble to mitigate/dampen the worst of the g-forces, while still leaving significant risk.
We'd probably need to define multiple interior states, e.g.: (i) active flight, (ii) supercruise (iii) parked in safe orbit, (iv) boarding submission (v) landed.
Captain can only leave his seat in (iii), (iv) and (v).
Captain controls whether other crew is able to leave their seats at own risk (including during (i)). It should be risky gameplay: crew dies/injures easily.
(ii), (iii) and (v) could be used for the more slow-paced gameplay: extended passenger/diplomacy/smuggling missions and crew loyalty missions, science/research/crafting gameplay, repairs, decontamination gameplay, varmint hunting, ship tweaking, basking on the observation deck.
(i) should just be used as 99% change to insta-die, with maybe some high-reward manoeuvres to pull.
(iv) should be a contained "safe" state which allows the crews of two ships to duke it out.