The purpose of fixing this is more so for mods at the oment but could be applied to the vanilla game later on.
This video shows here that this is possible with another vehicle class: http://www.youtube.com/watch?v=SHlSPg_SQYE and maybe by giving whatever the vehicle class has to allow it to move on a large ships to the man class cloud solve this issue.
A forum post for this issue exists here: http://forums.bistudio.com/showthread.php?166815-Discussion-of-problems-that-affect-walking-and-driving-on-drivable-ships-and-vehicles