ALiVE will persist vehicle only after a player enters and exits. So once you have a vehicle in place you need to jump in the drivers seat quickly to make it stay put. Same deal if the vehicle gets destroyed and respawns at base.

Respawnonstart is only really needed if you're using the BIS Spawn Template (to choose from multiple spawn points at mission start). With ALiVE's player location persistence it's better not to use it. You just need respawn="base" in description.ext and a marker named respawn_West in the mission.