To have the ability to lock stock from:

1. Other players breaking and entering your stock
2. Other players breaking your stock
3. No lock

It may also be useful to give access to specific players.
2 ideas to do this from me:

1. Right click on stock with a nametag renamed to a username (no nametag consumption)
   (Second time to remove player)
2. IR specific friends list via commands

Ops would ingore the lock however!

A tool to view who owns and has access a piece of rollingstock outside of OC
Specificly usefull for administration wanting to know who left there consist half on a switch and logged out. >:(