After much thought about this at work, I think I have come to determine what, to me, defines a vehicle.
Any device which provides an extended amount of inertial force and support to transport a person or object.
For example:
Shoes would not be a vehicle, because as the wearer, you must continually provide force in order to move (walking).
A skateboard IS a vehicle, because while you must provide the starting force, it will carry it on without continual work from the user.
Thus, for me, a parachute is a vehicle as it provides lateral inertial support during a decent, plus can be controlled to provide rotational support.
Keep discussing. This is a question without a clear answer, and seeing each persons views is very entertaining and enlightening.