Either some form of config entry or perhaps info stored on model that gives more direct control over where the player can access inventory of an object would be greatly appreciated. I think one good way that could be done would be a p3d selection in view geometry (invaccess for example) that basically dictates, if the player is within that mesh, they can see the inventory of the object.
This would even benefit internally as some objects you need to stand in a pinpoint precise location to access the inventory (like tents) and some are too large and can be accessed from several meters away (CivilianSedan).