This has been talked about a *lot* already. It's something most of us hope is in the works, but presumably is very low priority for the Devs. My personal ideas to help increase immersion were as follows:
Bunk (replaces the Undeathinator)
When occupied, it places the Player in a supine position. Fixes the Player in place relative to a Ship/Station but still allows them to look around. Sets the current re-spawn point for the player.
Chair
When occupied, it places the Player in a seated position. Fixes the Player in place relative to a Ship/Station but still allows them to look around. Can be linked to the following blocks:
Ship's Core - Allows remote control of the piloting functions of the Core (i.e. Flight Mode only) making it into a Pilot's Seat.*
Weapons Computer - Allows remote control of the Weapons Computer, making it a Tactical Station.
Docking Module - Allows remote control of the Core of any Turret docked to the Docking Module, making it into a Gunner's Chair.
Engineering Console (replaces the Build Block)
When occupied, it places the Player in a standing position. Fixes the Player in place relative to a Ship/Station and puts them into Build Mode. Can be linked to a Ship's Core and allows remote control of the construction functions of the Core (i.e. Build Mode only).*
*I'm thinking the Ship's Core should not be enterable
while a linked Chair or Console is already occupied.
All three of these blocks have actual practical purposes as well as aesthetic ones, and should promote the creation of functional interiors and cooperative crew activities at the cost of only 1 more block ID.