There is no way right now to get the coordinates of a position(driver, gunner, cargo,...) of a vehicle.

You can get memory point position with selectionPosition, but since vehicle positions are just defined as proxies and there are no mandatory existing memory points for them, there is no standar way to use it for this purpose.

The command could be something like:

getVehiclePositionCoords [ vehicle, posType, path]

Returns:
Position in model space, either the 3 points of the proxy triangle or the center of it.

Params:
Vehicle: self explanatory
posype: Position type, could be: "driver","gunner", "commander", "cargo", "turret"
path: if type is "cargo", a number indicating the cargo slot, if type is "turret"

This command could be usefull to implement new ways of 3d interaction with the vehicles. May look kindda a limited application, but a really cool one.

An alternative to this command and more generic could be a way to get generic proxy positions of a model. But that would be more complicated since some proxies are present on diferent LODs. But could be really cool to for example get the position where the weapons are attached on the vehicles (not sure if there is a memory point that could be used for those)