I see,
Never actually tried it myself .It was just the method that came to mind as I read your thread.
The Aluminium base so that the magnets were never able to repulse past the area of the base you'd want the vehicle in or tilt one side down where the effect was less ,and the fishing line to keep it from flying off the base.(as fishing line can be very strong and near invisible at the same time)

absolutely no idea if it'd work,it was just the first thing to rattle its way to the surface.
As Aircav's pointed out its one of those ideas that pops into many an addled mind.However yours has a more of a Blue thunder meets Aliens feel than the more Vietnam inspired versions Which is more my cup of tea.
Aircav's version is nice but it's all those bare arms Workshop does ,definitely not sculpted by someone who spends a lot of time in the out doors.Or maybe the future is devoid of bugs and beasties. Ah but what do I know
Still I'll keep watch your versions progress .
Mark.