Can a player swap position with a dead body in lifeboat?
The FAQ you linked to I believe covers this. Since fights are started by a character refusing a seat exchange, a dead person's seat is just taken from them.

How do I start a fight?
Fights can only be started by a character refusing a mugging or a seat exchange. Incapacitated characters (unconscious or dead) cannot start a fight, join a fight or have a fight fought on their behalf. If somebody wants to take something from them, it just happens.