One way you could do this is ray cast down when the player lands on a platform and store that platform as the respawn platform. How do you know when a player lands you ask? when you jump you could raycast down and get the distance to the platform, when this ... lets say less than 0.01 units the player has landed.
Hope that helps
BTW, did you mean the death object has to have a raycast on it's fsm? Or the player?
