The title should be pretty-selfexplanatory. There should be beds that allow you to sleep on a vehicle. This would make long-range exploration vehicles like ships more useful and practical in survival mode.

It could either be added as its own part, or this could simply be a new boolean value that seats could have.

If possible, it should use as much Vanilla code as possible to maintain compatibility with mods like Morpheus.
To get around the issue of respawning, for the respawn coordinates, instead of setting the coordinates of the vehicle it could just keep the existing coordinates, so you would still respawn next to your bed made from blocks.

I looked into this once, and found that unless the player is actually in a bed, they won't be considered sleeping. And the only way to get them in a bed is to click it, which runs the coordinate-setting code. There might be some way around this though, so I'll take another peek and report back if so.