The bottom is going to be armoured to an extent against bottoming out the car etc, so harder to do that (and have it be water/salt proof) through the floor I guess?
Having your battery eject itself because of a sensor failure while driving at 70mph would be exciting to everyone involved though!
A wind turbine automatically feathers. Why can't the airship automatically raise and lower itself?
With modern forecasting, getting it's height right shouldn't be too hard?